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Visit Castellum’s web site to download and subscribe to press releases and financial reports. castellum.com Q3 Interim report January– September 2026

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Key metrics 2026 Jul–Sep 2025 Jul–Sep 2026 Jan–Sep 2025 Jan–Sep LTM, Oct 2025 –Sep 2026 2025 Jan–Dec Income, SEK M 2,246 2,407 6,987 7,196 9,385 9,593 Net operating income, SEK M 1,614 1,702 4,829 4,908 6,444 6,524 Income from property management, SEK M 1,126 1,253 3,427 3,474 4,558 4,606 Net income for the period, SEK M 939 858 2,873 1,050 2,759 938 SEK per share, before and after dilution¹ 1.97 1.61 5.75 1.72 5.28 1.36 Return on equity, %, LTM 3.6 3.9 3.6 3.9 3.6 1.2 Net investment, SEK M −3,854 675 −7,452 3,498 −6,561 4,389 Net leasing, SEK M −5 16 105 −166 131 −140 Loan-to-value ratio, %² 37.4 36.5 37.4 36.5 37.4 36.5 Interest coverage ratio, multiple 3.0 3.5 3.1 3.2 3.1 3.2 EPRA NRV , SEK/share² 169 160 169 160 169 160 Energy performance, normalised, kWh/sq. m., LTM 86 87 86 87 86 85 Energy optimisation, like-for-like portfolio, normalised, %, LTM −1 −7 −1 −7 −1 −7 The period in brief Comparisons shown in brackets are made with the corresponding period in the previous year except in sections describing assets and liabilities, where comparisons are made with the end of the previous year. January–September 2026 ◼ Income totalled SEK 6,987 M (7,196). In the like-for-like portfolio, the change in rental income was −1.7 per cent (0.0), excluding currency effects. ◼ Net operating income (NOI) totalled SEK 4,829 M (4,908). Net operating income in the like-for-like portfolio decreased 3.6 per cent (−0.9), excluding currency effects. ◼ Income from property management totalled SEK 3,427 M (3,474), corresponding to SEK 7.39 per share (7.06). ◼ Changes in value of investment properties totalled SEK −684 M (−1,400), corresponding to −0.5 per cent (−1.0). The value of the property portfolio amounted to SEK 129 Bn (137) at the end of the period. ◼ Net income after tax for the period totalled SEK 2,873 M (1,050), corresponding to SEK 5.75 (1.72) per share1. ◼ New leases were concluded for 245,000 square metres (242,000) with an annual rent of SEK 659 M (532). Net leasing totalled SEK 105 M (−166) for the period and SEK 131 M (−143) for the last 12 months. ◼ Net investments totalled SEK −7,452 M (3,498), of which SEK 2,953 M (2,085) pertained to investments in existing properties, SEK — M (2,031) to acquisitions and SEK −10,405 M (−618) to divestments. ◼ Investments in associated companies and joint ventures totalled SEK — M (836). ◼ The loan-to-value ratio2 was 37.4 per cent (36.5). ◼ The interest coverage ratio for the latest twelve-month period was 3.1 (3.2) and interest-rate hedging (more than 1 year) was applied to 61 per cent (68) of the loan portfolio at the end of the period. July–September 2026 ◼ Income totalled SEK 2,246 M (2,407). In the like-for-like portfolio, the change in rental income was −0.9 per cent (−0.3), excluding currency effects. ◼ Net operating income (NOI) totalled SEK 1,614 M (1,702). Net operating income in the like-for-like portfolio decreased 1.1 per cent (−2.4), excluding currency effects. ◼ Income from property management totalled SEK 1,126 M (1,253), corresponding to SEK 2.55 per share (2.55). ◼ Changes in value of investment properties totalled SEK −953 M (−232), corresponding to −0.7 per cent (−0.2). ◼ Net income after tax for the period totalled SEK 939 M (858), corresponding to SEK 1.97 (1.61) per share1. ◼ New leases were concluded for 43,000 square metres (57,000) with an annual rent of SEK 83 M (143). Net leasing totalled SEK −5 M (16). ◼ Net investments totalled SEK −3,854 M (675), of which SEK 985 M (797) pertained to investments in existing properties, SEK — M (331) to acquisitions and SEK −4,839 M (−453) to divestments. Important events during the quarter ◼ During the quarter, 22,596,587, treasury shares were repurchased. Total treasury share repurchases during the period amounted to 61,616,281at an average price of SEK 122.74 per share, for a total of SEK 7,563 M. ◼ Castellum has once again been approved for Nasdaq Green Equity Designation and thereby retains its green equity designation. ◼ Under the company’s EMTN programme, Castellum has issued an unsecured bond loan of EUR 300 M. ◼ Castellum intends to move from four regions to two regions in Sweden. The change is part of Castellum’s continued efforts to simplify the organisation, make decisions faster and reduce its costs. Important events after the end of the period ◼ On 1 October, Castellum handed over the 95 properties that were divested to Wihlborgs at an agreed property value of SEK 13.3 Bn. ◼ At an Extraordinary General Meeting held on 14 October, it was resolved to reduce the share capital by SEK 24,005,225 through the cancellation of 46,541,184 treasury shares. To restore the share capital, it was simultaneously resolved to carry out a stock dividend issue in a corresponding amount. 1. The comparative figures for Earnings per share have been adjusted to include deductions for interest on the hybrid bond. Refer to page 7. 2. Includes Assets held for sale and Liabilities attributable to assets held for sale. Refer to page 10. 2 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026 Front page image: Norrköping, Knäppingsborg 7 This is a translation of the Swedish language original. In the events of any differences between this translation and the Swedish original, the latter shall prevail.

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“Back to Basics” continues We are adapting our organisation on the basis of the divestments made during the year. Our objective is to reduce our administration costs by 15 per cent, which corresponds to nearly SEK 100 M. In the meantime, we are simplifying our regions, moving from four to two: Region Svea and Region Göta. This will result in less bureau- cracy – and thus greater efficiency. Net leasing SEK 105 M Net leasing was SEK −5 M during the quarter, and SEK 105 M for the period. The period included both major new leases and major termi- nations – for example, we signed a new lease with Ericsson in Hagastaden for SEK 140 M, while AFRY terminated its lease in Solna for SEK −95 M. Excluding the new lease to Ericsson in the Infinity project property in Hagastaden, net leasing was negative by approx- imately SEK 35 M. The rental market has thus not yet turned around – at least not for Castellum. Occupancy rate 87.3 per cent The occupancy rate fell by 0.2 percentage points during the quarter, and has declined by 1.9 percentage points since the start of the year. The primary cause is the negative net leasing during earlier periods. Rental income in the like-for-like portfolio −1.7 per cent The falling occupancy rate has led to declines in both rental income (1.7 per cent) and net operating income (3.6 per cent) in the like-for- like portfolio. Only when we reverse the downward trend in occu- pancy rates will we be able to see higher rental income and higher net operating income in the like-for-like portfolio. Growth in rental income is the key factor in achieving our target of 10 per cent return on equity. That is why I put a heavy emphasis on leasing, leasing and leasing. Income from property management per share increased by 5 percent Despite the decline in income from property management com- pared with previous year, income from property management per share increased from SEK 7.06 to 7.39 per share. This corresponds to an increase of 5 percent, attributable to share buy-backs. Change in values on properties SEK −700 M Our asset portfolio has lost almost SEK 700 M in value during the year, driven primarily by changed expectations regarding future cash flows and then chiefly assumptions about vacancies, which are taking longer to fill than previously assumed. The yield require- ment was largely unchanged during the year. Buy-back for SEK 7.6 Bn or 62 million shares During the period we repurchased 62 million shares, which corre- sponds to a buy-back of SEK 7.6 Bn. Last week, an extraordinary shareholders’ meeting gave its approval for additional buy-backs. On 1 October, Castellum handed over the property portfolio that were divested to Wihlborgs at an agreed property value of SEK 13.3 Bn. Of the amount, we intend to use approximately SEK 8 Bn for share buy-backs and approximately SEK 5 Bn for debt repayment. We are retaining the properties that we believe we can manage well, and divesting the properties that we believe others could manage better than we can. To date in 2026, we have sold properties for SEK 25 Bn at prices slightly above their carrying amounts. We will lease premises, maintain control over our costs and gen- erate a return for our shareholders. Our objective is a return on equity of at least 10 per cent over a business cycle. Pål Ahlsén Chief Executive Officer 3 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Condensed consolidated statement of comprehensive income SEK M 2026 Jul–Sep 2025 Jul–Sep 2026 Jan–Sep 2025 Jan–Sep LTM, Oct 2025 –Sep 2026 2025 Jan–Dec Rental and service income 2,246 2,407 6,987 7,196 9,385 9,593 Income 2,246 2,407 6,987 7,196 9,385 9,593 Operating costs −298 −306 −1,077 −1,077 −1,401 −1,400 Maintenance −83 −75 −250 −214 −390 −354 Property tax −141 −151 −433 −435 −577 −578 Lease and property administration costs −110 −173 −398 −562 −573 −737 Net operating income 1,614 1,702 4,829 4,908 6,444 6,524 Central administrative costs −29 −41 −86 −176 −173 −264 Income from participations in associated companies and joint ventures −260 58 −568 568 −370 767 Net financial items Net interest items −564 −506 −1,644 −1,556 −2,170 −2,082 Leasing cost/site leasehold fees −16 −18 −42 −54 −59 −71 Income including associated companies and joint ventures 745 1,195 2,489 3,690 3,672 4,874 of which income from property management¹ 1,126 1,253 3,427 3,474 4,558 4,606 Changes in value Properties −953 −232 −684 −1,400 −1,735 −2,450 Financial holdings — — — −4 — −4 Goodwill −124 −21 −242 −60 −323 −141 Derivatives 958 140 1,070 −869 994 −945 Income before tax 626 1,082 2,633 1,357 2,608 1,334 Current tax −30 −120 −161 −262 −156 −257 Deferred tax 343 −104 401 −45 307 −139 Net income for the period 939 858 2,873 1,050 2,759 938 Average number of shares, thousands 440,952 492,102 463,868 492,272 470,985 492,229 Earnings, SEK per share before and after dilution² 1.97 1.61 5.75 1.72 5.28 1.36 Other comprehensive income (OCI) 2026 Jul–Sep 2025 Jul–Sep 2026 Jan–Sep 2025 Jan–Sep LTM, Oct 2025 –Sep 2026 2025 Jan–Dec Net income for the period 939 858 2,873 1,050 2,759 938 Items that may be reclassified to net income for the period Translation difference of currencies 682 −40 1,476 −158 1,162 −472 Currency hedging −118 27 −391 130 −316 204 Comprehensive income for the period 1,503 845 3,958 1,022 3,605 670 1. For calculation, refer to Alternative performance measures on pages 26–28. 2. The comparative figures for Earnings per share have been adjusted to include deductions for interest on the hybrid bond. Refer to page 7. 4 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Performance analysis Income Income totalled SEK 6,987 M (7,196). The change of SEK –209 M is attributable to income in the like-for-like portfolio decreased by SEK –110 M, corresponding to –1.7 per cent, which is attributable primarily to increased vacancies of SEK –147 M. Furthermore, the divestment of United Spaces lowered income by SEK –115 M and income from development properties has attributed with SEK 33 M. Income from transactions attributed with SEK 16 M and includes non-recurring income of SEK 84 M pertaining to derecognition of a capitalised annuity in a property sale. Development of income SEK M 2026 Jan–Sep 2025 Jan–Sep Change, % Like-for-like portfolio 6,411 6,521 −1.7 Development properties 133 100 Transactions 456 440 Coworking — 183 Group elimination — −48 Currency adjustment¹ −13 — Total income 6,987 7,196 −2.9 1. The current year, restated with the exchange rate of the comparison period. Costs Property costs amounted to SEK 2,158 M (2,129). Costs in the like- for-like portfolio increased SEK 53 M, corresponding to 2.7 per cent excluding currency effects. The cost increase in the like-for-like portfolio is attributable primarily to higher costs of SEK 20 M for snow removal, SEK 26 M for heating, SEK 24 M for maintenance and SEK 12 M for property insurance. However, these cost increases are offset to some extent by lower costs from rent losses, which decreased by SEK 42 M. Furthermore, a shift of costs between property administration and central administration costs had a negative impact of SEK 49 M on property costs. This shift is the result of the new division of responsibilities between central functions and the regional property management organisations that was established in late 2025. The new cost allocation has applied as of 2026, and comparative figures have not been restated. Lease and property administration amounted to SEK 398 M (562). This decrease of SEK 164 M is related in part to reduced costs of SEK 159 M relating to the divestment of United Spaces and by streamlining at the head office and a general review of costs. The decrease is offset by increased cost attributable to the aforemen- tioned cost shift. Central administration costs amounted to SEK 86 M (176), a decrease of SEK 90 M, with SEK 41 M being attributable to a general review of costs and the remainder attributable to the aforemen- tioned cost shift. Development of costs SEK M 2026 Jan–Sep 2025 Jan–Sep Change, % Like-for-like portfolio 2,032 1,979 2.7 Development properties 59 57 Transactions 71 93 Currency adjustment¹ −4 — Total property costs 2,158 2,129 1.4 Coworking — 207 Group elimination — −48 Central administration costs 86 176 Total costs 2,244 2,464 −8.9 1. The current year, restated with the exchange rate of the comparison period. Property costs, 12 months, SEK/sq. m., LTM¹ SEK M Offices Public sector Warehouse/ Light industry Retail Total Operating costs 333 249 192 183 270 Maintenance 83 73 59 49 72 Property tax 151 89 32 92 104 Property administration 129 98 91 105 113 Total 696 509 374 429 559 Q3 2025, LTM 676 489 323 437 542 1. Starting in 2026, the table presents key metrics as LTM, which is a change from earlier when the calculation of these key metrics was reported on a full-year basis. The comparative figures have also been restated. Segment information Castellum’s operations are organised, governed and reported in geographical regions. United Spaces was divested in 2025, which resulted in the elimination of the Coworking segment. The difference between net operating income of SEK 4,829 M (4,908) and income before tax of SEK 2,633 M (1,357) comprises central administrative costs of SEK –86 M (–176), earnings of SEK –568 M (568) from associated companies and joint ventures, net financial items of SEK –1,686 M (–1,610) and SEK 144 M (–2,333) in changes in values on properties, financial holdings, goodwill and derivatives. Income Net operating income SEK M 2026 Jan–Sep 2025 Jan–Sep 2026 Jan–Sep 2025 Jan–Sep Stockholm 1,776 1,792 1,291 1,303 West1 1,455 1,373 1,041 975 Central 1,323 1,342 917 948 Mälardalen 958 962 636 643 Öresund 1,009 1,085 681 760 Finland 466 507 263 302 Coworking — 183 — −23 Group elimination — −48 — — Total 6,987 7,196 4,829 4,908 1. The 2026 figures includes non-recurring revenue of SEK 84 M pertaining to reversal of accrued annuity. 5 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Income from associated companies and joint ventures Income from associated companies and joint ventures consists of Castellum’s share of Entra ASA’s and Halvorsäng Fastighets AB’s earnings. Castellum’s share of the associated companies’ and joint ventures’ income from property management is included in the line item “of which income from property management” . As of the balance sheet date, an impairment was made owing to lower net reinstatement value in Entra. The exchange-rate impact on the Entra holding is recognised in OCI. For further information on Entra and Halvorsäng, refer to page 9. SEK M 2026 Jan–Sep 2025 Jan–Sep Income from property management 369 352 Change in values on properties −787 91 Tax 49 −92 Other −31 −48 Castellum’s share of earnings from associated companies and joint ventures −400 303 Impairment/reversal of impairment −168 265 Total impact on net income for the period −568 568 Translation difference 1,399 −264 Currency hedging −513 207 Total impact on comprehensive income for the period 318 511 Net financial items Net financial items totalled SEK −1,686 M (−1,610). During the third quarter, interest costs were impacted by SEK 21 M in non- recurring costs pertaining to the redemption of loans linked to sales of prop- erties. SEK M 2026 Jan–Sep 2025 Jan–Sep Financial income 15 26 Interest costs, loans −1,644 −1,585 Interest income and expenses, interest rate derivatives 57 157 Interest income and expenses, currency derivatives −104 −177 Less: Capitalised interest 36 37 Other financial costs −6 −13 Exchange rate differences 2 −1 Total net interest costs −1,644 −1,556 Leasing cost/site leasehold fees −42 −54 Total net financial items −1,686 −1,610 The average closing interest rate for the loan portfolio, including interest-rate and currency hedging with long maturities, was 3.5 per cent (3.1) on the balance sheet date. The average interest rate provides a snapshot of the latest fixed-interest period for the derivative and loan portfolios on the balance sheet date and excludes certain items in net financial items such as the accrual of borrowing costs, other financial costs, currency hedging with short maturities and, in some cases, currency effects. Income from property management Income from property management totalled SEK 3,427 M (3,474), corresponding to SEK 7.39 per share (7.06). The decrease in income from property management is attributable to increased vacancies and higher net interests costs. Castellum’s participations in associated companies and joint ventures added SEK 369 M (352) to income from property management, of which SEK 359 M (350) pertained to Entra and SEK 10 M (2) pertained to Halvorsäng. Changes in value Properties Castellum reports changes in value of SEK –684 M (–1,400). Un- realised changes in value of SEK amounted to –446 M (–1,412) during the period, with changes in cash flow having a negative impact and project gains having a positive one. The average exit yield for Castellum’s portfolio totalled 5.73 per cent at the end of the period – 9 basis points higher than in the preceding quarter. The increase is partly driven by the sale of two large properties in central Stockholm, with the divested properties having had low yield requirements relative to the Group average. During the period, 16 per cent of the property value was externally valued. The external valuations are on par with the internal valuations, confirming Castellum’s assessed market value. Castellum’s property divestments completed during the period resulted in a realised change in value of SEK –238 M. Net sale price amounted to SEK 10,404 M after deduction for deferred tax, other deductions and transaction costs of SEK –413 M. The total underly- ing property value in the divestments was thus SEK 10,817 M, a difference of SEK 175 M compared with the latest assessment of SEK 10,642 M. SEK M 2026 Jan–Sep 2025 Jan–Sep Cash flow −1,319 −1,716 Project gains/building rights 863 290 Yield requirement 10 −173 Acquisitions — 187 Unrealised changes in value −446 −1,412 % of property value at start of year −0.3 −1.0 Divestments −238 12 Total change in value −684 −1,400 % of property value at start of year −0.5 −1.0 Goodwill Changes in goodwill totalled SEK −242 M (−60), of which SEK −184 M (−20) is attributable to divestments and SEK −58 M (−40) is attribut- able to negative developments in value of properties. Derivatives Castellum holds both interest rate and currency derivatives. In profit for the period, the derivatives generated a change in value of SEK 1,070 M (−869), which includes realised changes in value of SEK 17 M (60) and unrealised changes in value of SEK 1,053 M (−929). Changes in value resulting from hedging relationships totalled SEK –391 M (130) and are reported in OCI. 6 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Tax Total tax for the period was SEK 240 M (–307), of which SEK –161 M (–262) pertained to current tax. Applying the nominal tax rate to income before tax, the total theoretical tax is SEK –542 M. The difference of SEK 782 M is due primarily to deferred tax on divested properties and non-deductible interest. The remaining tax loss carry forwards, estimated at SEK 54 M (351), are restricted for use in parts of the Group. Tax calculation January–September 2026 SEK M Basis current tax Basis deferred tax Income from property management 3,427 Less: Associated companies and joint ventures −369 Deductions for tax purposes: depreciation −1,643 1,643 reconstructions −641 641 Hybrid bond −335 335 Non-deductible interest 1,308 — Other tax items −252 51 Taxable income from property management 1,495 2,670 Tax on income from property management −308 Divestment of properties — −5,595 Change in values on properties — −217 Change in values on derivatives −416 898 Taxable income before tax loss carry forwards 1,079 −2,244 Tax loss carry forwards, opening balance −351 351 Tax loss carry forwards, closing balance 54 −54 Taxable income 782 −1,947 Tax according to the income statement −161 401 Earnings per share Earnings per share amounted to SEK 5.75 (1.72) The increase is mainly attributable to value changes and a lower average number of shares outstanding. 2026 Jan–Sep 2025 Jan–Sep Net income for the period, SEK M 2,873 1,050 interest on hybrid bond after tax, SEK M −206 −201 Adjusted net income for the period, SEK M 2,667 849 Weighted average number of shares, thousands 463,868 492,272 Earnings per share, before and after dilution, SEK 5.75 1.72 Return on equity Castellum’s overall financial goal is for return on equity to total at least 10 per cent per year over a business cycle. At 30 September 2026, return on equity for LTM was 3.6 per cent (3.9). Target — 10% return on equity Moreover, Castellum reports an adjusted return measurement, with the hybrid bond being reported as a debt instrument. Adjusted return on equity for LTM was 3.6 per cent (4.0). The diagram below shows the outcomes of the two different return measurements. Comparison classifying hybrid as debt instrument1 -20 -15 -10 -5 0 5 10 15 20 25 2021 Q3 2022 2023 2024 2025 2026 Return on equity, LTM, % Return on equity, hybrid as liability, LTM, % 1. The hybrid bond was issued in August 2021. -20 -15 -10 -5 0 5 10 15 20 25 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 Return on equity, LTM, % Return on equity, average 5 years, % Return on equity, average 10 years, % Target, 10% 7 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Condensed consolidated balance sheet Change in equity SEK M 30 Sep 2026 30 Sep 2025 31 Dec 2025 ASSETS Investment properties 115,973 137,328 136,919 Goodwill 3,511 4,247 4,166 Right-of-use assets 1,023 1,407 1,105 Participations in associated companies and joint ventures 11,662 11,064 10,905 Derivatives 2,395 1,373 1,281 Other fixed assets 127 162 133 Other receivables 1,281 1,522 1,260 Cash and cash equivalents 159 137 120 Assets held for sale 13,985 — — Total assets 150,116 157,240 155,889 EQUITY AND LIABILITIES Equity 74,443 78,663 78,311 Deferred tax liability 13,181 14,974 15,139 Other provisions 19 32 75 Derivatives 438 425 576 Interest-bearing liabilities 56,287 57,497 57,019 Lease liabilities 1,023 1,407 1,105 Non-interest bearing liabilities 3,023 4,242 3,664 Liabilities attributable to assets held for sale 1,702 — — Total equity and liabilities 150,116 157,240 155,889 Attributable to Parent Company shareholders SEK M Number of shares out- standing, thousands Share capital Other capital contribution Currency translation reserve Currency hedge reserve Retained earnings Hybrid bond Total equity Equity, 31 Dec 2024 492,446 246 38,942 210 −290 29,905 10,161 79,174 Dividend (SEK 2.48/share) — — — — — −1,221 — −1,221 Dividend, hybrid bond — — — — — −349 — −349 whereof tax effect — — — — — 72 — 72 Repurchase of treasury shares −344 — — — — −39 — −39 Share price-related remuneration — — — — — 4 — 4 Net income, Jan-Sep 2025 — — — — — 1,050 — 1,050 OCI, Jan-Sep 2025 — — — −158 130 — — −28 Equity, 30 Sep 2025 492,102 246 38,942 52 −160 29,422 10,161 78,663 Share price-related remuneration — — — — — 0 — 0 Net income, Oct–Dec 2025 — — — — — −112 — −112 OCI, Oct–Dec 2025 — — — −314 74 — — −240 Equity, 31 Dec 2025 492,102 246 38,942 −262 −86 29,310 10,161 78,311 Dividend, hybrid bond — — — — — −335 — −335 whereof tax effect — — — — — 69 — 69 Repurchase of treasury shares −61,616 — — — — −7,563 — −7,563 Cancellation of treasury shares — −8 — — — 8 — 0 Stock dividend issue — 8 — — — −8 — 0 Share price-related remuneration — — — — — 3 — 3 Net income, Jan-Sep 2026 — — — — — 2,873 — 2,873 OCI, Jan-Sep 2026 — — — 1,476 −391 — — 1,085 Equity, 30 Sep 2026 430,486 246 38,942 1,214 −477 24,357 10,161 74,443 8 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Comments on the balance sheet Investment properties As of 30 September 2026, Castellum owns a total of 644 properties (673) at a fair value of approximately SEK 129 Bn (137). Changes in the property portfolio Carrying amount, SEK M Number Property portfolio on 1 Jan 2026 136,919 673 Acquisitions 0 — Investments in existing properties 2,953 — Divestments −10,642 −19 Property settlements — −10 Unrealised changes in value −446 — Currency translation 509 — Property portfolio on balance sheet date 129,293 644 Less: Assets held for sale −13,320 −95 Closing carrying amount 115,973 549 Goodwill Castellum recognises total goodwill of SEK 3,924 M (4,166) attribut- able to business combinations, with the difference between con- tractual tax and nominal deferred tax being recognised as goodwill. Changes in goodwill arise primarily when properties that were included in the transactions have been divested, or in the event of a larger drop in property values. SEK M 30 Sep 2026 31 Dec 2025 Opening carrying amount 4,166 4,307 Divestments −184 −24 Impairment −58 −117 Total 3,924 4,166 Less: Assets held for sale −413 — Closing carrying amount 3,511 4,166 Participations in associated companies and joint ventures At the end of the period, Castellum owned 67,305,119 shares in Entra ASA, corresponding to 37.1 per cent of both the capital and the votes. Furthermore, Castellum owns 50 per cent of the capital and voting rights in Halvorsäng Fastighets AB. Castellum recognises its holdings in accordance with the equity method. Entra is valued on the basis of EPRA NRV . An impairment test of this participation is conducted every quarter. SEK M 30 Sep 2026 31 Dec 2025 Opening carrying amount 10,905 9,924 Acquisitions — 770 Shareholders’ contributions — 66 Share of associated company and joint venture earnings −400 433 Dividend received −74 −69 Impairment/reversal of impairment −168 334 Currency translation 1,399 −553 Closing carrying amount 11,662 10,905 Entra Halvorsäng SEK M 2026 Jan–Sep 2025 Jan–Sep 2026 Jan–Sep 2025 Jan–Sep Rental income 2,324 2,192 21 — Income from property management 967 947 20 4 Net income for the period −1,083 844 17 39 Of which minority share 17 78 — — Entra Halvorsäng 30 Sep 2026 31 Dec 2025 30 Sep 2026 31 Dec 2025 Number of properties 79 80 1 1 Property value, SEK M 62,230 56,596 992 863 Leasable area, thousand sq. m. 1,115 1,117 53 53 Economic occupancy rate, % 93.8 93.9 91.9 91.9 WAULT, years 5.8 6.0 11.6 11.6 Interest-bearing liabilities, SEK M 32,027 28,307 100 — Debt maturity, years 3.8 3.6 0.7 — Fixed interest term, years 3.5 3.4 0.2 — Loan-to-value ratio, % 49.0 48.0 neg — EPRA NRV , SEK/share 166 155 — — Share price, NOK/share 97.70 115.60 — — Carrying amount, SEK M 11,168 10,420 494 485 9 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Deferred tax Deferred tax liability totalled SEK 14,529 M (15,139). An estimated fair value can be calculated at SEK 2,586 M (2,422), refer to the assumptions in the 2025 Annual Report. SEK M Basis Nominal tax liability Real tax liability Tax loss carry forwards 54 11 11 Derivatives −1,242 −256 −234 Untaxed reserves −931 −192 −173 Properties −77,075 −15,896 −2,190 Total −79,194 −16,333 −2,586 Properties, asset acquisitions 8,751 1,804 — Total −70,443 −14,529 −2,586 Less: Liabilities attributable to assets held for sale 6,550 1,348 371 Closing carrying amount −63,893 −13,181 −2,215 Derivatives At 30 September 2026, the market value of the derivative portfolio amounted to SEK 1,957 M (705), divided into SEK 1,314 M (776) for interest rate derivatives and SEK 643 M (–71) for currency deriva- tives. Fair value is established according to IFRS 13, level 2. Disposal group held for sale On June 24, Castellum signed an agreement to divest 95 properties located in Malmö, Lund, Helsingborg, Ängelholm and Burlöv. The closing date was 1 October. The divestment involves a large portfo- lio in the Öresund segment. The divestment group is classified as being held for sale in accordance with IFRS 5. The assets and liabili- ties included in this divestment group are specified below. SEK M 30 Sep 2026 Assets held for sale Investment properties 13,320 Goodwill 413 Right-of-use assets 101 Other fixed assets 10 Other receivables 137 Cash and cash equivalents 4 Closing carrying amount 13,985 Liabilities attributable to assets held for sale Deferred tax liability 1,348 Other provisions 1 Lease liabilities 101 Non-interest bearing liabilities 252 Closing carrying amount 1,702 10 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Asset portfolio Castellum is one of the Nordic region’s leading commercial prop- erty companies. The portfolio is concentrated in attractive growth cities in Sweden as well as Copenhagen and Helsinki. Through the associated company Entra, Castellum is also exposed to attractive areas in Norway. Common for Castellum’s properties is that they are located in or near city centre locations, have good means of communication and supplementary services. Castellum’s geographical focus combined with stable tenants, for example state and municipal operations, provides good condi- tions for stability and long-term growth. Our commercial portfolio consists largely of offices (63 per cent), followed by warehouse/light industry (16 per cent), public sector properties (12 per cent), and retail (5 per cent). The remaining 4 percent consists of developments and undeveloped land. Castellum’s property portfolio at 30 September 2026 comprised 644 properties (673) with a total contract value of SEK 8,463 M (9,299) and a total leasable area of 5,124,000 square metres (5,291,000). Economic occupancy rate The economic occupancy rate was 87.3 per cent, compared to 89.2 per cent at the end of 2025. Of this 1.9 percentage-point decrease, 0.2 percentage points pertains to properties sold with a high eco- nomic occupancy rate. The remainder of the decline is due to rising vacancy rates. As of 2026, a new definition of economic occupancy rate has been applied, refer to page 29. The comparative figures have been adjusted. Investments During the period, Castellum invested SEK 2,953 M (2,085) in exist- ing properties, of which SEK 1,527 M (805) pertains to new con- struction, extensions and reconstructions; SEK 843 M (764) to tenant adaptations; SEK 75 M (105) to energy investments, SEK 450 M (401) to maintenance investments and SEK 58 M (10) to other investments. -5 000 -4 500 -4 000 -3 500 -3 000 -2 500 -2 000 -1 500 -1 000 -500 0 500 1 000 Stockholm West Central Mälardalen Öresund Finland Acquisitions Property sales Investments in existing properties Property value by region Property value by category Net investment Net investment, SEK M 2026 Jul–Sep 2025 Jul–Sep 2026 Jan–Sep 2025 Jan–Sep LTM, Oct 2025 –Sep 2026 2025 Jan–Dec Acquisitions — 331 — 2,031 54 2,085 Investments in existing properties 985 797 2,953 2,085 4,083 3,215 Total investments 985 1,128 2,953 4,116 4,137 5,300 Divestments −4,839 −453 −10,405 −618 −10,698 −911 Net investments −3,854 675 −7,452 3,498 −6,561 4,389 Proportion of the property value, % −2.9 0.5 −5.4 2.6 −4.8 3.2 Stockholm, 30% West, 20% Central, 18% Mälardalen, 13% Öresund, 10% Finland, 5% Denmark, 4% Office, 63% Warehouse/Light Industry, 16% Public Sector Properties, 12% Retail, 5% Projects and Land, 4% Divestments Region Disposal date Area, thousand sq. m. Annual rental value, SEK M Net sale price, SEK M Hållstugan 28 Central Q1 2026 8 16 170 AP7 portfolio (8 properties)¹ Several Q2 2026 103 257 5,016 Linköping portfolio (3 properties) Central Q2 2026 10 17 245 Alecta portfolio (2 properties) Stockholm Q3 2026 36 226 4,825 1. One divestment of one property remains to be closed; this is expected to take place in Q4. Significant property disposals in 2026 Net investments per region 11 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Property portfolio The difference between the net operating income of SEK 4,575 M reported above and the NOI of SEK 4,829 M in the statement of profit or loss is attributable to the fact that divested properties have been excluded from the table. 30 Sep 2026 January–September 2026 Category Number Area, thousand sq. m. Property value, SEK M SEK/sq. m. Rental value, SEK M SEK/sq. m.¹ Economic occupancy rate, % Income, SEK M Property costs, SEK M SEK/sq. m.¹ Net operating income, SEK M OFFICES Stockholm 53 644 26,288 40,840 1,450 2,812 84.8 1,197 333 679 864 West 74 457 13,448 29,413 723 2,106 87.7 617 205 626 412 Central 67 521 12,015 23,046 809 2,043 84.0 675 234 597 441 Mälardalen 31 375 10,879 29,043 663 2,356 84.4 555 168 627 387 Öresund 30 256 8,115 31,680 498 2,584 80.8 436 145 721 291 Denmark 12 128 5,326 41,772 270 2,804 88.0 231 63 677 168 Finland 17 196 5,722 29,185 523 3,476 83.9 443 189 1,294 254 Total Office 284 2,577 81,793 31,745 4,936 2,492 84.7 4,154 1,337 696 2,817 PUBLIC SECTOR PROPERTIES Stockholm 6 119 3,623 30,386 204 2,253 94.6 192 42 472 150 West 16 132 2,747 20,749 185 1,845 93.1 171 48 529 123 Central 22 249 7,441 29,852 419 2,312 88.2 376 93 513 283 Mälardalen 4 37 744 20,140 50 1,790 96.7 47 14 511 33 Öresund 4 34 743 21,693 57 2,225 89.9 52 10 397 42 Denmark 1 8 196 25,909 13 2,372 97.6 13 6 1,152 7 Total Public sector properties 53 579 15,494 26,730 928 2,156 91.2 851 213 509 638 WAREHOUSE/LIGHT INDUSTRY Stockholm 27 179 3,585 20,029 197 1,472 87.9 181 57 447 124 West 78 577 8,206 14,223 496 1,146 93.6 456 133 327 323 Central 17 100 1,156 11,523 86 1,132 94.1 80 26 347 54 Mälardalen 26 376 4,315 11,487 349 1,441 92.6 309 123 447 186 Öresund 36 261 2,904 11,127 213 1,080 89.1 186 64 326 122 Finland 1 — 78 — 7 — 93.6 6 1 — 5 Total Warehouse/Light industry 185 1,493 20,244 13,560 1,348 1,253 91.8 1,218 404 374 814 RETAIL Stockholm 9 79 2,031 25,789 119 2,006 94.6 108 21 352 87 West 10 64 1,368 21,321 85 1,761 98.1 82 19 414 63 Central 18 128 1,984 15,551 149 1,534 91.2 132 42 431 90 Mälardalen 7 36 662 18,121 45 1,628 97.6 42 12 430 30 Öresund 15 68 1,236 18,200 89 1,757 85.2 71 25 522 46 Total Retail 59 375 7,281 19,419 487 1,721 92.8 435 119 428 316 Total 581 5,024 124,812 24,843 7,699 2,028 87.3 6,658 2,073 559 4,585 Projects 23 100 3,812 91 13 25 −12 Undeveloped land 40 — 669 10 5 3 2 Total investment properties² 644 5,124 129,293 7,800 6,676 2,101 4,575 31 Dec 2025 673 5,291 136,919 — — — — January–September 2025 — — — 8,150 7,127 2,133 4,994 1. Calculated solely based on the area attributable to investment properties. 2. Includes Assets held for sale, refer to page 10. 12 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Larger projects Ongoing projects over SEK 100 M Castellum has a portfolio of larger ongoing projects with an aggregate investment of SEK 3.2 Bn, with SEK 1.1 Bn remaining to be invested. The average occupancy rate in these projects is 81 per cent. A total of three projects were completed during the year, with a total rental value of SEK 125 M and an occupancy rate of 100 per cent. Projects approved but not started Category Type Location Project start Area, sq. m. Annual rental value, SEK M Economic occupancy rate, % Total investment, SEK M Of which invested, SEK M Remaining to invest, SEK M Gladan 5 & 7 O R Stockholm Q4 2026 6,200 32 0 221 46 175 Total projects not started 6,200 32 0 221 46 175 Ongoing projects Category Type Location Completed Area, sq. m. Annual rental value, SEK M Economic occupancy rate, % Total investment, SEK M Of which invested, SEK M Remaining to invest, SEK M Örnäs 1:28 (Brunna B3) W N Stockholm Q1 2027 13,100 15 0 229 190 39 Tingstadsvassen 31:2 I N Gothenburg Q1 2027 5,900 9 54 101 48 53 Sunnanå 8:511 W N Malmö Q1 2027 22,400 26 0 282 228 54 Götaland 5 (Werket) P R/E Jönköping Q2 2027 7,700 20 100 166 79 87 Blandaren 18 O R/E Linköping Q3 2027 5,000 13 83 147 53 94 Hotellet 8 H R Jönköping Q4 2027 7,400 24 100 197 73 124 Sorbonne 1 (Infinity) O N Stockholm Q4 2027 24,000 143 98 1,800 1,320 480 Amasonen 3 O R Linköping Q4 2027 10,300 33 91 271 115 156 Total ongoing projects 95,800 283 81 3,193 2,106 1,087 Developments completed or fully/partly occupied Category Type Location Completed Area, sq. m. Annual rental value, SEK M Economic occupancy rate, % Total investment, SEK M Of which invested, SEK M Remaining to invest, SEK M Rotterdam 1 O R Stockholm Q3 2026 17,100 74 100 300 288 12 Solsten 1:172 O R/E Gothenburg Q3 2026 15,100 34 100 131 106 25 Gullbergsvass 1:15 H R Gothenburg Q1 2026 4,500 17 100 100 99 1 Total completed projects 36,700 125 100 531 493 38 Sum total projects 138,700 440 81 3,945 2,645 1,300 Category: O=Office, W=Warehouse, Lo=Logistics, P=Public sector, I=Industry, Re=Retail, H=Hotel, OTH=Other Investment type: N=New construction, R=Reconstruction, E=Extension 1. Included in Assets held for sale, refer to page 10. 13 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Tenants Castellum’s exposure to individual tenants is very low, with a lease portfolio that has a large spread across many different tenants, cus- tomer sizes and industries. This spreads the risk for rent losses and vacancies. The Group has approximately 7,000 commercial leases and 400 residential leases, and their distribution in terms of size is presented in the table below. The single largest lease accounts for 1.3 per cent of the Group’s total rental income, while the corresponding figure for the single largest tenant is 2.3 per cent. As at 30 September 2026, the remaining average length of contract was 3.3 years (3.6). Net leasing, January–September 20261 SEK M Stockholm West Central Mälardalen Öresund Finland Total New leasings Investment properties 116 77 92 64 123 19 491 Development properties 140 5 22 1 0 0 168 Total 256 82 114 65 123 19 659 Terminated Existing properties −193 −91 −77 −36 −112 −30 −539 Bankruptcies −1 −3 −8 0 −3 0 −15 Total −194 −94 −85 −36 −115 −30 −554 Net leasing 62 −12 29 29 8 −11 105 January–September 2025 −26 30 2 −76 −103 7 −166 1. Includes Assets held for sale, refer to page 10. Lease size Number of leases Contract value, SEK M Proportion of value, % Commercial, size <0.25 3,061 199 2 0.25–0.5 954 348 4 0.5–1.0 1,189 837 10 1.0–3.0 1,217 2,095 25 >3.0 607 4,762 56 Total commercial 7,028 8,241 97 Residential 400 44 1 Parking spaces and other 5,822 178 2 Total 13,250 8,463 100 Largest tenants Contract value, SEK M Share of total contract value, % AFRY 195 2.3 The Swedish Police Authority 132 1.6 The Swedish Social Insurance Agency 131 1.5 Handelsbanken 126 1.5 ABB 124 1.5 E.ON Nordic 92 1.1 Hitachi 78 0.9 The Swedish state, through the Swedish Fortifications Agency 74 0.9 Nokia Solutions and Networks AM Oy 69 0.8 Biz Apartments 60 0.7 Total 1,081 12.8 Lease maturity structure Number of leases Contract value, SEK M Proportion of value, % Commercial, term 2026 1,048 357 4 2027 2,283 1,696 20 2028 1,393 1,829 22 2029 1,265 1,561 18 2030 549 906 11 >2030 490 1,892 22 Total commercial 7,028 8,241 97 Residential 400 44 1 Parking spaces and other 5,822 178 2 Total 13,250 8,463 100 Net leasing During the period, Castellum signed leases with an annual rental value of SEK 659 M (532). Notices of termination amounted to SEK –554 M (–698), of which SEK –15 M (–111) were bankruptcies and SEK –122 M (–42) were notices of termination with more than 18 months left of contract. Net leasing for the period thus totalled SEK 105 M (–166). The time difference between reported net leasing and the income effect thereof is estimated to be between 6–15 months in investment properties and 12–24 months for devel- opment properties. Normally, the impact of reported bankruptcies on earnings is immediate. Annual rent corresponding to SEK 181 M (197) was renegotiated during the period, with an average change in rent of –2.5 per cent (1.6). Leases valued at SEK 898 M (1,345) were extended with no changes to terms. 14 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Financing During the quarter, an unsecured bond loan of EUR 300 M was issued on the European capital market at a credit margin of 0.78 per cent and a fixed annual coupon of 3.75 per cent. The bond has a tenor of three years and matures on September 3, 2029. The average interest rate remained unchanged at 3.5 per cent during the quarter. The proportion of interest-bearing liabilities hedged (more than 1 year) on the balance sheet date was 61 per cent (68). Average Stibor 3m was 2.03 per cent during the quarter, compared to 2.04 per cent during Q2 2026. Interest rate maturity structure, 30 September 2026 Maturity date Interest-bearing liabilities,SEK M Share, % Average interest rate, % Average fixed interest rate term, years 0–1 year 21,785 39 5.3² 0.1 1–2 years 3,249 6 2.0 1.5 2–3 years 8,351 15 2.2 2.6 3–4 years 4,950 9 2.2 3.5 4–5 years 6,552 11 2.6 4.5 >5 years 11,400 20 2.3 6.9 Total 56,287 100 3.5 2.7 Credit maturity structure, 30 September 2026 Maturity date Bank credit, SEK M Bonds, SEK M Commercial paper, SEK M Total interest-bearing liabilities, SEK M Share, % Unutilised credit facilities, SEK M Total available credit facilities, SEK M 2026 429 728 2,699 3,856 7 421 4,277 2027 337 3,021 1,210 4,568 8 — 4,568 2028 5,016 4,998 — 10,014 18 9,369 19,383 2029 4,964 7,537 — 12,501 22 1,206 13,707 2030 2,032 7,172 — 9,204 16 2,959 12,163 >2030 14,197 1,947 — 16,144 29 38 16,182 Total 26,975 25,403 3,909 56,287 100 13,993 70,280 Key metrics – interest-bearing financing1 30 Sep 2026 30 Sep 2025 31 Dec 2025 Interest-bearing liabilities, SEK M 56,287 57,497 57,019 Bank credit, SEK M 26,975 23,064 22,320 Bonds outstanding, SEK M 25,403 30,826 30,695 Commercial paper outstanding, SEK M 3,909 3,607 4,004 Cash and cash equivalents, SEK M 163 137 120 Unutilised credit facilities, SEK M 13,993 22,905 20,176 Unencumbered assets ratio, % 61.4 52.2 55.8 Secured debt to total assets ratio, % 17.7 14.6 14.2 Loan-to-value ratio, % 37.4 36.5 36.5 Interest coverage ratio, LTM, multiple 3.1 3.2 3.2 Net debt/EBITDA, LTM, multiple 8.9 9.1 9.1 Average debt maturity, years 4.0 4.6 4.3 Average fixed interest rate term, years 2.7 3.5 3.3 Credit rating – S&P Terminated, June 2026 BBB, Stable Outlook BBB, Stable Outlook Credit rating – Moody’s Baa2, Stable Outlook Baa2, Stable Outlook Baa2, Stable Outlook Average effective rate excluding unutilised credit facilities, % 3.5 3.1 3.1 Average effective rate including unutilised credit facilities, % 3.5 3.3 3.2 Market value interest rate derivatives, SEK M 1,314 595 776 Market value currency derivatives, SEK M 643 353 −71 1. Includes Assets held for sale and Liabilities attributable to assets held for sale. Refer to page 10. 2. Includes the margin for the entire floating rate portion of the debt portfolio. The average value for floating rate liabilities amounted to 3.3 per cent (3.4). 15 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Castellum’s financial policy and commitments in EMTN programmes Policy Commitments in EMTN programme Outcome Loan-to-value ratio Not to permanently exceed 40%. Not exceeding 65% 37.4% Interest coverage ratio, LTM At least 3 At least 1.5 3.1 Secured debt to total assets ratio Not exceeding 45% 18% Funding risk • average debt maturity, years At least 2 years 4.0 years • proportion maturing within 1 year No more than 30% of loans outstanding and unutilised credit agreements 7% • Liquidity reserve Liquidity reserve corresponding to 12 months’ impending loan maturities Achieved Interest rate risk • average interest duration 1.5–4.5 years 2.7 years • maturing within 6 months No more than 50% 37% Credit and counterparty risk • rating restriction Credit institutions with high ratings, at least S&P BBB+ Achieved Currency risk • net exposure in foreign currency Maximum 10 per cent of balance sheet total Achieved Sensitivity analysis Change Effect on Amount, SEK M Economic occupancy rate +/–1 ppt Income from property management +102/−102 Rental income +/− 1% Income from property management +89/−89 Property costs +/− 1% Income from property management −28/+28 Underlying market rates +/–1 ppt Income from property management −218/+218 Exit yield +/– 0.25 ppt Investment properties¹ −5,323/+5,813 1. Includes Assets held for sale, refer to page 10. Allocation of interest-bearing liabilities, 30 September 2026 Secured and unsecured credits, 30 September 2026 Bank credit, SEK 26,975 M Bonds, SEK 25,403 M Commercial paper, SEK 3,909 M Unsecured credits, SEK 29,674 M Secured credits, SEK 26,613 M 16 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Consolidated cash flow statement The cash flow statement has been prepared according to the indirect method. SEK M 2026 Jul–Sep 2025 Jul–Sep 2026 Jan–Sep 2025 Jan–Sep LTM, Oct 2025 –Sep 2026 2025 Jan–Dec Net operating income 1,614 1,702 4,829 4,908 6,444 6,524 Central administrative costs −29 −41 −86 −176 −173 −264 Adjustments for non-cash items 4 15 −46 80 5 131 Interest received 3 11 10 23 23 36 Interest paid −561 −542 −1,677 −1,677 −2,268 −2,268 Tax paid −19 −10 −223 −50 −308 −135 Cash flow from operating activities before change in working capital 1,012 1,135 2,807 3,108 3,723 4,024 Change in current receivables 86 239 13 −162 258 83 Change in current liabilities −224 −168 −84 −74 −196 −186 Cash flow from operating activities 874 1,206 2,736 2,872 3,785 3,921 Investments in existing properties −971 −786 −2,917 −2,049 −4,034 −3,166 Property acquisitions — −292 0 −323 −53 −376 Indirect property acquisitions — — — −1,645 0 −1,645 Sales of properties — — 58 — 98 40 Indirect property sales 4,792 352 10,269 509 10,529 769 Acquisition of other fixed assets, net −6 0 −8 −5 −15 −12 Dividend received from associated companies — — 74 — 143 69 Investments in associated companies and joint ventures — — — −836 0 −836 Other investments — — — −4 0 −4 Cash flow from investment activities 3,815 −726 7,476 −4,353 6,668 −5,161 Repurchase of treasury shares −3,000 — −7,563 −39 −7,563 −39 Dividend paid — −305 −305 −610 −611 −916 Dividend paid, hybrid bond — — −335 −349 −335 −349 Drawn loans 10,003 4,637 37,085 15,088 43,744 21,747 Repayment of loans −11,395 −4,809 −38,636 −15,148 −45,289 −21,801 Derivatives −237 −39 −416 303 −373 346 Cash flow from financing activities −4,629 −516 −10,170 −755 −10,427 −1,012 Cash flow for the period 60 −36 42 −2,236 26 −2,252 Cash and cash equivalents opening balance 98 174 120 2,400 137 2,400 Exchange-rate difference in cash and cash equivalents 5 −1 1 −27 0 −28 Total cash and cash equivalents 163 137 163 137 163 120 Less: Assets held for sale −4 — −4 — −4 — Cash and cash equivalents at end of period 159 137 159 137 159 120 Average number of shares, thousands 440,952 492,102 463,868 492,272 470,985 492,229 Cash flow before changes in working capital, SEK/share 2.30 2.31 6.05 6.31 7.90 8.18 17 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Key metrics 2026 Jan–Sep 2025 Jan–Sep 2025 Jan–Dec 2024 Jan–Dec 2023 Jan–Dec 2022 Jan–Dec 2021 Jan–Dec Property-related key metrics Rental value, SEK/sq. m.¹ 2,028 2,053 2,072 2,019 1,927 1,758 1,648 Property cost, SEK/sq. m.¹ 559 542 551 542 547 511 425 Net operating income, SEK/sq.m. ¹’² 1,231 1,282 1,274 1,275 1,209 1,048 1,008 Surplus ratio, %² 69.1 70.0 69.0 70.1 68.5 67.2 70.7 Economic occupancy rate, %¹ 87.3 88.7 89.2 91.1 91.0 93.4 92.9 Leasable area at end of period, t sq.m 5,124 5,306 5,291 5,282 5,485 5,696 5,853 Number of properties at end of period 644 677 673 672 709 749 762 Property value at the balance sheet date, SEK/sq. m 24,843 25,614 25,538 25,475 25,258 26,737 26,667 Financial key metrics Return on total capital, %, LTM 2.4 3.5 2.8 2.8 −6.6 0.6 8.6 Return on equity, %, LTM 3.6 3.9 1.2 3.0 −14.8 2.2 22.7 Loan-to-value ratio, %³’⁴ 37.4 36.5 36.5 35.6 37.4 42.3 39.2 Loan-to-value ratio, property, %³’⁴ 43.4 41.8 41.6 41.4 43.3 49.5 45.5 Interest coverage ratio, multiple, LTM 3.1 3.2 3.2 3.3 3.0 3.9 5.2 Average effective rate excluding unutilised credit facilities, % 3.5 3.1 3.1 3.2 3.0 2.6 1.8 Data per share Share price at end of period, SEK 124.25 106.30 106.40 120.55 143.30 106.06 204.81 Equity, SEK 173 160 159 161 157 202 206 Earnings, SEK³ 5.75 1.72 1.36 4.22 −26.30 3.74 34.86 Income from property management, SEK 7.39 7.06 9.36 9.78 9.69 11.45 10.46 Cash flow before changes in working capital, SEK 6.05 6.31 8.18 8.90 9.06 10.24 9.73 Dividend, SEK — — — 2.48 — — 6.38 Number of shares outstanding at end of period, thousands 430,486 492,102 492,102 492,446 492,601 390,933 405,384 Average number of shares, thousands 463,868 492,272 492,229 492,515 451,377 393,849 336,784 Key metrics according to EPRA⁴’⁵ EPRA EPS, SEK 6.72 6.63 8.95 9.32 9.49 11.09 9.73 EPRA NRV , SEK 169 160 160 157 154 203 211 EPRA NTA, SEK 163 156 155 152 149 193 202 EPRA NDV , SEK 140 132 131 131 127 165 166 EPRA LTV , % 51.7 50.5 50.4 49.4 52.1 55.6 51.4 EPRA vacancy rate, % 11.6 10.3 10.3 8.8 7.9 6.7 7.8 1. Amended definition as of 2026. Comparative figures have been restated. 2. Excluding other income of SEK 65 M for the period January–December 2024. 3. The comparative figures for Earnings per share have been adjusted to include deductions for interest on the hybrid bond. Refer to page 7. 4. Includes Assets held for sale and Liabilities attributable to assets held for sale. Refer to page 10. 5. For calculations and definitions, refer to pages 26–29. 18 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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80 90 100 110 120 20122013201420152016201720182019202020212022202320242025 2026 Q3Heating, cooling and building electricity (normalised) kWh/sq.m. Sustainability Sustainability results Over the latest twelve-month period, the normalised energy consump- tion in the like-for-like portfolio decreased by 1.0 per cent. In Q3 2026, the climate impact from investment properties amounted to 3.79 kg CO₂e/sq m, compared with the 2026 interim target of 3.66 kg CO₂e/sq m. The increase is due primarily to higher emissions factors among district heating providers. This interim target is part of Castellum’s long-term goal of achieving net-zero emissions by 2040. The proportion of sustainability-certified properties continued to increase. At the end of the third quarter of 2026, 310 properties – corre- sponding to 61 per cent of the property area – had been certified. Over the latest twelve-month period, energy optimisation projects totalling just over SEK 120 M had either been concluded or started. The average yearly investment over the last five years amounted to approximately SEK 200 M. Castellum’s venture in fossil-free energy is continuing through the extended “100 on Solar” solar PV programme. The target is to have 200 solar PV systems in operation by 2030. At the end of Q3 2026, Castellum has constructed 135 solar PV systems, whose output corresponds to approximately 26 per cent of Castellum’s annual electricity needs. Castellum has been approved for the Green Equity Designation on Nasdaq Stockholm and thereby retains its green equity designation. This year’s external audit by S&P Global Shades of Green notes that 81 per cent of Castellum’s turnover comes from energy-efficient build- ings, which exceeds Nasdaq’s 50 per cent threshold. S&P also esti- mates that 78 per cent of Castellum’s investments in 2025 were green. Sustainability goals and strategy Castellum’s sustainability strategy, The Sustainable City, encompasses measurable targets in three areas of focus: Future-proofed assets, Sustainable workplaces and Sound business. This strategy has been integrated into the business model and encompasses investments in attractive, inclusive workplaces as well as responsible business with clear procedures for ethics, regulatory compliance and the supply chain. By combining environmental, social and governance-related aspects, Castellum is strengthening its competitiveness and long-term profitability while the company promotes a more sustainable society. Examples from our operations In Q3 2026, Castellum purchased EvoBuild concrete – a carbon capture and storage (CCS) product – from Heidelberg Materials for its warehouse and logistics project. This concrete reduces its carbon foot- print by capturing and permanently storing carbon during production at Brevik in Norway. Re-use is a priority area. In Region West, materials in 126 projects were either dropped off or picked up through the REbygg re-use hub in Gothenburg up through the third quarter. This has helped prevent just over 200 metric tons of CO₂e in emissions and reduced costs by SEK 1.1 M compared with the purchase of new materials. In the Rotterdam 1 project, extensive re-use efforts – including re-use of lighting fixtures, glass partitions, wall materials, doors, kitchens, pipes, and ventilation ducts – have helped prevent 111 metric tons of CO₂e in emissions. At the same time, costs decreased by SEK 2 M com- pared with the purchase of new materials. Energy use over time, kWh/sq. m. 0 25 50 75 100 0 100 200 300 400 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 Q3No. of sustainability-certified properties Share of sustainability-certified area, % % Sustainability-certified properties 0 2 4 6 8 10 12 14 202320242025 2026 Q3 20272028202920302031203220332034203520362037203820392040 Castellum’s climate target 2040, investment properties¹ The sector's roadmap towards net-zero climate-related emissions (SBTi) Status kg CO₂e per sq.m., year Castellum’s climate target 2040, investment properties1,2 0 10 20 30 0 30 60 90 120 150 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 Q3 No. of Solar PV systems Installed power, MW MW Solar PV systems 1. Includes Assets held for sale and Liabilities attributable to assets held for sale. Refer to page 10. 2. Scope 1, 2 and tenant emissions in electricity (Scope 3.13) 19 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Castellum’s rating: 74/100 (the only Nordic property company to be included) Castellum’s rating: AAA 1 THE USE BY Castellum OF ANY MSCI ESG RESEARCH LLC OR ITS AFFILIATES (“MSCI”) DATA, AND THE USE OF MSCI LOGOS, TRADEMARKS, SERVICE MARKS OR INDEX NAMES HEREIN, DO NOT CONSTITUTE A SPONSORSHIP , ENDORSEMENT, RECOMMENDATION, OR PROMOTION OF Castellum BY MSCI. MSCI SERVICES AND DATA ARE THE PROPERTY OF MSCI OR ITS INFORMATION PROVIDERS, AND ARE PROVIDED ‘AS-IS’ AND WITHOUT WARRANTY . MSCI NAMES AND LOGOS ARE TRADEMARKS OR SERVICE MARKS OF MSCI. INFORMATION PROVIDERS, AND ARE PROVIDED ‘AS-IS’ AND WITHOUT WARRANTY . MSCI NAMES AND LOGOS ARE TRADEMARKS OR SERVICE MARKS OF MSCI. 1 Castellum works with science-based climate targets in line with the Paris Agreement. Castellum’s rating: Gold Castellum’s rating: Low-carbon leader Ratings Key metrics – Sustainability Q3 2026, LTM 2025 2024 Resource efficiency Total energy performance, kWh/sq. m. per year 85 80 91 Total energy performance, normalised, kWh/sq. m. per year 86 85 93 1. of which actual heating 60 55 62 2. of which normalised heating 61 60 64 3. of which electricity and cooling 25 25 29 Energy efficiency, like-for-like portfolio, LTM, normalised, % −1 −7 −4 Energy efficiency, like-for-like portfolio, LTM, actual energy use, % 3 −10 −7 Taxonomy-aligned investment properties, proportion of the property value, % 49 54 48 Total water use, m³/sq. m., year 0.2 0.2 0.3 Water savings/yr, like-for-like portfolio, LTM, % −7 −7 0 Fossil-free Share of non-fossil energy (purchased), % 99 99 99 Non-fossil fuel powered vehicles, % 100 100 99 Number of charging posts for electric vehicles 1,635 1,627 1,453 Number of solar PV systems installed 135 130 116 Climate-related emissions (kg CO₂e/sq. m., year Scope 1 0.1 0.1 0.1 Scope 2 – market-based 1.5 1.0 0.9 Scope 2 – location-based 3.5 3.3 4.0 Sustainability certification Sustainability certification, % of sq. m. 61 58 54 Social key metrics Number of employees on balance sheet date 478 485 564 Equality, women/men, % 39/61 42/58 43/57 Sick leave, % (long- and short-term) 2.5 2.7 2.6 Number of injuries leading to absence, employees¹ 0 0 1 Injury frequency rate (LTIFR), employees¹ 0 0 0.9 Number of injuries leading to absence, contractors¹ 12 12 2 Injury frequency rate (LTIFR), contractors¹ 2.3 2.3 0.4 Interns, % of employees YTD 10 13 7 ESG benchmarks MSCI ESG Score TBA AAA AAA S&P CSA points (0–100) TBA 74 76 CDP mark (A to D- rating) TBA A- A 1 This key metric is calculated on a full-year basis and refers to 2025. Castellum’s rating: A- 20 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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The Castellum share Source: Shareholder statistics from Modular Finance AB. Data collected and analysed from Euroclear, Morningstar, Finansinspektionen, Nasdaq and Millistream. Castellum is listed on Nasdaq Stockholm Large Cap. At the end of the year, the company had just over 87,000 shareholders. The 15 single largest shareholders as of 30 September 2026 are presented in the table below. Shareholders as of 30 September 2026 Shareholders Number of shares, thousands Share of capital, % Share of votes, % Akelius Apartments Ltd 126,000 26.4 29.3 Gösta Welandson with companies 19,638 4.1 4.6 Vanguard 16,779 3.5 3.9 BlackRock 16,265 3.4 3.8 Nordea Funds 14,848 3.1 3.4 Folksam 11,514 2.4 2.7 Alecta Tjänstepension 9,400 2.0 2.2 Handelsbanken Fonder 8,912 1.9 2.1 Länsförsäkringar Fonder 8,183 1.7 1.9 APG Asset Management 8,055 1.7 1.9 Swedbank Robur Fonder 5,706 1.2 1.3 State Street Investment Mgmt 4,502 0.9 1.0 SEB Funds 3,674 0.8 0.9 Carnegie Funds 3,431 0.7 0.8 Avanza Pension 3,265 0.7 0.8 15 largest owners 260,172 54.5 60.4 Swedish shareholders, other 135,924 28.5 31.6 Foreign shareholders, other 34,390 7.2 8.0 Total shares outstanding 430,486 90.1 100.0 Treasury shares 47,041 9.9 Total shares registered 477,526 100.0 Buy-back and cancellation of own shares During the period, a buy-back programme of own shares was initi- ated and was concluded later during the period. The purpose of the buy-backs is to adjust the company’s capital structure and thereby efficiently promote an increase in shareholder value. During the quarter, 22,596,587 treasury shares were repur- chased. In total 61,616,281 treasury shares were repurchased during the period at an average price of SEK 122.74 per share including transaction costs, corresponding to an overall value of SEK 7,563 M. 15,075,097 treasury shares were also retired during the period. In order to restore share capital after the cancellation, a stock dividend issue in an amount of SEK 7.5 M – corresponding to the amount by which the share capital had been reduced through cancellation of own shares – was carried out. The company’s holding of treasury shares at the end of the period thus amounted to 47,040,587 shares, corresponding to 9.9 per cent of the number of shares registered at the end of the period. Dividend The 2026 Annual General Meeting resolved that no dividend would be paid for financial year 2025. Key share metrics 30 Sep 2026 31 Dec 2025 Share price, SEK 124.25 106.40 Market capitalisation, SEK Bn 53.5 52.4 Turnover, millions¹ 84 386 Turnover rate, %¹ 72 79 Dividend yield — 2.3 1. From the starts of the respective years. Pertains to turnover on Nasdaq Stockholm. Shareholders by country, 30 September 2026 Sweden, 49% Cyprus, 25% USA, 12% Finland, 4% Other, 10% 21 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Parent Company Condensed income statement SEK M 2026 Jul–Sep 2025 Jul–Sep 2026 Jan–Sep 2025 Jan–Sep 2025 Jan–Dec Income 64 66 172 199 251 Central administrative costs −68 −87 −220 −295 −428 Income before financial items −4 −21 −48 −96 −177 Income from Group companies 89 118 544 1,485 1,591 Income from associated companies 389 67 822 283 182 Financial income 565 858 1,588 2,773 2,426 Financial costs −739 −931 −2,007 −2,720 −2,366 Income before changes in value and tax 300 91 899 1,725 1,656 Changes in value Financial holdings — — — −4 −4 Derivatives 808 144 591 −673 −661 Income after changes in value 1,108 231 1,490 1,048 991 Appropriations −2 — −2 — −30 Income before tax 1,106 231 1,488 1,048 961 Tax −142 −56 −119 −43 −157 Net income for the period 964 175 1,369 1,005 804 Other comprehensive income (OCI) 2026 Jul–Sep 2025 Jul–Sep 2026 Jan–Sep 2025 Jan–Sep 2025 Jan–Dec Net income for the period 964 175 1,369 1,005 804 Items that may be reclassified to net income for the period Currency hedging — 18 −10 −31 −27 Comprehensive income for the period 964 193 1,359 974 777 Condensed balance sheet SEK M 30 Sep 2026 30 Sep 2025 31 Dec 2025 Participations in Group companies 40,887 51,686 41,729 Participations in associated companies and joint ventures 11,587 11,009 10,839 Receivables, Group companies 54,466 53,146 54,492 Derivatives 2,395 1,373 1,281 Other assets 122 86 104 Cash and cash equivalents 82 25 21 Total assets 109,539 117,325 108,466 Equity 41,819 48,484 48,286 Deferred tax liability 206 83 156 Derivatives 438 425 576 Interest-bearing liabilities 49,367 40,893 40,972 Liabilities, Group companies 17,274 26,447 17,734 Non-interest bearing liabilities 435 993 742 Total equity and liabilities 109,539 117,325 108,466 The Parent Company is Castellum Aktiebolag (publ). The contingent liabilities decreased by SEK 8,980 M during the period as a result of the repayment of external debt in subsidiaries for which Castellum AB had provided guarantees during the year. As of 30 September 2026 the contingent liabilities amounted to SEK 6,589 M (15,569). The contingent liabilities are attributable to guarantees provided for subsidiaries. 22 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Other information Risks and uncertainties Castellum’s operations, earnings and financial position are impacted by a number of risk factors. These are related primarily to properties, tax and financing. The company works actively to identify and manage the risks and opportunities that are of material significance to its opera- tions. Castellum manages these risks brought about by a changing market by having a strong balance sheet and maintaining a low loan-to- value ratio. Combined with active asset management, the company reduces the risk for increased cost of capital. On the operational side, Castellum is working with a carefully composed tenant portfolio with a spread across notice periods, industries, tenant size and geographic location concentrated in growth cities. To facilitate risk management, Castellum has chosen to classify risks into the categories of business environment risks, operational risks, financial risks, and sustainability risks. More information on Castellum’s risks and their management can be found in the Annual Report for 2025. Forward-looking information A number of items recognised in this report are forward-looking, and the actual outcome may differ substantially. Apart from the factors that have expressly been commented on, other factors such as economic growth, interest-rate levels, financing terms, yield requirements on property assets and political decisions may also have a material impact on the actual outcome. Accounting policies Castellum’s consolidated financial statements are prepared in accor- dance with the International Financial Reporting Standards (IFRS). The interim report has been prepared in accordance with IAS 34 Interim Financial Reporting, and for the Parent Company in accordance with Chapter 9 of the Annual Accounts Act. Moreover, the relevant provi- sions in the Annual Accounts Act and the Securities Markets Act have been applied. For the Group and the Parent Company, the same accounting policies and bases for calculation as in the latest annual report have been applied. In addition to the financial statements, disclosures in accordance with IAS 34.16A appear in the remainder of this interim report. Preparation of the interim report requires company management to make assessments and estimates, and to make assumptions that have impacted the application of the accounting policies and the recognised amounts of assets, liabilities, income and costs. The actual outcome may deviate from these estimates and assessments. The critical assessments made and the sources of uncertainty in existing estimates are the same as those in the latest published annual report. Earnings per share is calculated by dividing net income for the year attributable to Parent Company shareholders, less interest to hybrid bond holders, by the weighted average number of common shares out- standing during the year. The company has no outstanding instruments that would entail a dilution of earnings per share. The Swedish properties in the Öresund region have been classified as a divestment group held for sale in accordance with IFRS 5. The assets and liabilities concerned are reported separately in the state- ment of financial position. The reclassification has impacted the presentation of the balance sheet but has not impacted the Group’s earnings or the calculation of key metrics. The introduction of IFRS 18, which will replace IAS 1 on 1 January 2027, will result in changes to the presentation and disclosures in the financial statements. Castellum is currently in a preparatory imple- mentation phase. Drafts for future reporting structures have been developed and relevant policy choices in accordance with the new standard have been evaluated. Necessary system adjustments have also been identified and prepared. Valuation of the asset portfolio Castellum internally assesses its entire property holdings on a quar- terly basis, corresponding to level 3 in IFRS 13. According to accepted theory, the value of an asset is the net present value of the future cash flows that the asset is expected to generate. This section aims to describe and illustrate Castellum’s cash flow-based model for calcula- tion of the value of the property portfolio. The value of the property portfolio is calculated in a 10 to 20-year cash flow model as the total present value of net operating income minus remaining investments on ongoing projects, during the calculation period of 10 to 20 years, and the present value of the estimated residual value after the cash-flow period. The residual value comprises the present value of all future net operating income after the cash-flow period. The estimated market value of undeveloped land and building rights are added to this. Accordingly, valuation is conducted pursuant to IFRS 13, level 3. The assessment pertaining to the future earnings and the yield require- ment, which are the weightiest value-driving factors in the valuation model, are crucial for the calculated value of the property portfolio. The yield requirement is derived from market transactions on objects of equal value, known as the local price method. The earnings are based on existing contracts and the most likely lease scenarios in the respec- tive properties. For further information on Castellum’s valuation of its property portfolio, refer to Note 10 in the Annual Report for financial year 2025. Valuation of financial assets and liabilities To calculate the fair value of our interest-rate and currency derivatives, market rates for each term and exchange rates as quoted in the market for the closing date are used. Interest rate swaps are valued by dis- counting future cash flows to present value. When calculating the fair value of derivatives, adjustments are made for counterparty risk in the form of Credit Value Adjustments (CVA) and Debit Value Adjustments (DVA). CVA shows Castellum’s risk of experiencing credit loss in the event of counterparty default, whereas DVA shows the opposite. The adjustment is calculated at the counterparty level based on expected future credit exposure, risk of default and the recovery rate of exposed credits. Related-party transactions Remuneration has been paid to Board members and senior executives pertaining to work performed. Related-party transactions also encompass Castellum invoicing SEK 0.8 M for services performed pertaining to project management and administration to Halvorsäng, which is a joint venture together with Göteborgs Hamn AB. During the period, Castellum received a divi- dend of NOK 74 M from Entra. All related-party transactions took place at arm’s length. 23 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Signing of the Report Gothenburg, 22 October 2026 The CEO hereby gives their assurance that the interim report provides a true and fair view of the Parent Company’s and Group’s operations, financial position and results and as well as the significant risks and uncertainties facing the company and companies within the Group. This information is information that Castellum Aktiebolag is obligated to make public pursuant to the EU Market Abuse Regulation. The information was sub- mitted for publication through the agency of the contact person set out above at 8:00 a.m. CEST on 22 October 2026. Pål Ahlsén Chief Executive Officer Independent Auditor’s Report on the review of interim financial information To the Board of Directors and the Chief Executive Officer of Castellum Aktiebolag (publ), Corporate ID No. 556475–5550 Introduction We have reviewed the interim report for Castellum Aktiebolag (publ) for the period January 1 - September 30, 2026. The board of directors and the President are responsible for the preparation and presentation of this interim report in accordance with IAS 34 and the Annual Accounts Act. Our responsibility is to express a conclusion on this interim report is based on our review. Scope of Review We conducted our review in accordance with the International Standard on Review Engagements ISRE 2410, Review of Interim Financial Information prepared by the Independent Auditor of the Entity. A review consists of making inquiries, primarily of persons responsible for financial and accounting matters, and applying analytical and other review procedures. A review has a different focus and is substantially less in scope than an audit conducted in accordance with ISA and generally accepted auditing standards. The procedures performed in a review do not enable us to obtain a level of assurance that would make us aware of all significant matters that might be identified in an audit. Therefore, the conclusion expressed based on a review does not give the same level of assurance as a conclusion expressed based on an audit. Conclusion Based on our review, nothing has come to our attention that causes us to believe that the interim report is not, in all material respects, pre- pared for the Group in accordance with IAS 34 and the Annual Accounts Act, and for the Parent Company in accordance with the Annual Accounts Act. Gothenburg, 22 October 2026 Deloitte AB Harald Jagner Authorized Public Accountant 24 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Quarterly summary 2026 Jul–Sep 2026 Apr–Jun 2026 Jan–Mar 2025 Oct–Dec 2025 Jul–Sep 2025 Apr–Jun 2025 Jan–Mar 2024 Oct–Dec Income statement, SEK M Income 2,246 2,420 2,321 2,398 2,407 2,403 2,386 2,444 Property costs −632 −724 −802 −783 −705 −769 −814 −792 Net operating income 1,614 1,696 1,519 1,615 1,702 1,634 1,572 1,652 Central administrative costs −29 −32 −24 −87 −41 −70 −66 −63 Income from associated companies and joint ventures −260 −349 40 198 58 322 188 152 Net interest items −564 −556 −524 −526 −506 −516 −534 −558 Leasing cost/site leasehold fees −16 −9 −17 −17 −18 −20 −16 −24 Income including associated companies and joint ventures 745 750 994 1,183 1,195 1,350 1,144 1,159 Changes in value Properties −953 −147 416 −1,051 −232 −800 −368 5 Financial holdings — — — — — — −4 −5 Goodwill −124 −111 −8 −81 −21 −18 −21 −60 Derivatives 958 −225 338 −76 140 −417 −592 934 Current tax −30 −69 −63 5 −120 −40 −102 −2 Deferred tax 343 436 −378 −94 −104 114 −55 −42 Net income for the period 939 634 1,299 −114 858 189 2 1,989 Other comprehensive income 564 3 519 −240 −13 −21 7 85 Comprehensive income for the period 1,503 637 1,818 −354 845 168 9 2,074 Balance sheet, SEK M Investment properties 115,973 120,548 138,141 136,919 137,328 136,999 135,020 135,711 Goodwill 3,511 3,634 4,158 4,166 4,247 4,268 4,286 4,307 Participations in associated companies and joint ventures 11,662 11,269 11,645 10,905 11,064 10,996 10,311 9,924 Derivatives 2,395 1,369 1,645 1,281 1,373 1,342 1,561 2,539 Other assets 2,431 2,538 2,941 2,498 3,091 3,354 3,322 2,978 Cash and cash equivalents 159 93 104 120 137 174 207 2,400 Assets held for sale 13,985 13,982 — — — — — — Total assets 150,116 153,433 158,634 155,889 157,240 157,133 154,707 157,859 Equity 74,443 75,939 77,892 78,311 78,663 77,815 78,906 79,174 Deferred tax liability 13,181 13,597 15,380 15,139 14,974 14,879 15,004 14,900 Derivatives 438 526 573 576 425 518 540 245 Interest-bearing liabilities 56,287 55,783 59,547 57,019 57,497 57,881 54,880 58,633 Other liabilities 4,065 4,260 5,242 4,844 5,681 6,040 5,377 4,907 Liabilities attributable to assets held for sale 1,702 3,328 — — — — — — Total equity and liabilities 150,116 153,433 158,634 155,889 157,240 157,133 154,707 157,859 Key metrics Earnings for the period, SEK/share¹ 1.97 1.22 2.52 −0.37 1.61 0.25 −0.13 3.90 Return on equity, %, LTM 3.6 3.4 2.9 1.2 3.9 3.4 3.3 3.0 Net investments, SEK M −3,854 −4,277 679 891 675 2,465 358 −307 Net leasing, SEK M −5 28 82 26 16 2 −184 23 Economic occupancy rate, %² 87.3 87.5 88.0 89.2 88.7 89.3 89.9 91.1 Loan-to-value ratio, %³ 37.4 37.3 37.5 36.5 36.5 36.7 35.3 35.6 Interest coverage ratio, multiple, LTM 3.1 3.2 3.2 3.2 3.2 3.2 3.2 3.3 EPRA NRV , SEK/share³ 169 167 164 160 160 159 159 157 1. The comparative figures for Earnings per share have been adjusted to include deductions for interest on the hybrid bond. Refer to page 7 2. Amended definition as of 2026. Comparative figures have been restated. 3. Includes Assets held for sale and Liabilities attributable to assets held for sale. Refer to page 10. 25 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Alternative performance measures A number of the financial alternative performance measures pre- sented by Castellum are not defined in accordance with the IFRS accounting standards. However, the company believes that these metrics provide useful supplementary information both to investors and to Castellum management, as they facilitate evaluation of company performance. It is to be noted that, since not all compa- nies calculate financial key metrics in the same manner, these are not always comparable to metrics used by other companies. These financial metrics should therefore not be seen as a substitute for metrics defined according to IFRS. Unless otherwise stated, the table below presents metrics, along with their reconciliation, which are not defined according to IFRS. Furthermore, definitions for these metrics also appear on page 29. The calculation of key metrics includes balance sheet items reported as Assets held for sale and Liabilities attributable to assets held for sale in accordance with IFRS 5 (refer to page 10) to ensure comparability and a fair view of the underlying operations. 2026 Jul–Sep 2025 Jul–Sep 2026 Jan–Sep 2025 Jan–Sep LTM, Oct 2025– Sep 2026 2025 Jan–Dec Average number of shares, thousands 440,952 492,102 463,868 492,272 470,985 492,229 Income from property management SEK M SEK/ share SEK M SEK/ share SEK M SEK/ share SEK M SEK/ share SEK M SEK/ share SEK M SEK/ share Income before tax 626 1.42 1,082 2.20 2,633 5.68 1,357 2.76 2,608 5.54 1,334 2.71 Reversed: Income from associated companies exclud- ing income from property management 381 0.86 58 0.12 938 2.02 −216 −0.44 886 1.88 −268 −0.54 Change in values on properties 953 2.16 232 0.47 684 1.47 1,400 2.84 1,735 3.68 2,450 4.98 Change in values on financial holdings — 0.00 — — — 0.00 4 0.01 — 0.00 4 0.01 Change in value on goodwill 124 0.28 21 0.04 242 0.52 60 0.12 323 0.69 141 0.29 Change in values on derivatives −958 −2.17 −140 −0.28 −1,070 −2.31 869 1.77 −994 −2.11 945 1.92 Income from property management 1,126 2.55 1,253 2.55 3,427 7.39 3,474 7.06 4,558 9.68 4,606 9.36 Current tax on income from property management −24 −0.05 −132 −0.27 −308 −0.66 −210 −0.43 −296 −0.63 −198 −0.40 EPRA Earnings/EPRA EPS 1,102 2.50 1,121 2.28 3,119 6.72 3,264 6.63 4,262 9.05 4,408 8.95 Return on equity LTM, Oct 2025– Sep 2026 LTM, Oct 2024 – Sep 2025 2025 Jan–Dec Earnings after tax 2,759 3,039 938 Average equity 77,050 78,333 78,574 Return on equity, % 3.6 3.9 1.2 Return on equity when classifying hybrid as debt instrument LTM, Oct 2025– Sep 2026 LTM, Oct 2024 – Sep 2025 2025 Jan–Dec Earnings after tax 2,759 3,039 938 Added: Coupon as interest −335 −348 −348 Earnings after tax including coupon as interest 2,424 2,691 590 Average equity 77,050 78,333 78,574 Less: average hybrid −10,161 −10,163 −10,161 Less: tax effect impacting equity −186 −101 −130 Average equity excluding hybrid bond 66,703 68,069 68,283 Return on equity when classifying hybrid as debt instrument, % 3.6 4.0 0.9 26 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Return on total capital LTM, Oct 2025– Sep 2026 LTM, Oct 2024 – Sep 2025 2025 Jan–Dec Income before tax 2,608 3,390 1,334 Reversed: Net interest items 2,170 2,114 2,082 Change in values on derivatives −994 −65 945 Net 3,784 5,439 4,361 Average total capital 155,062 156,654 156,566 Return on total capital, % 2.4 3.5 2.8 Interest coverage ratio 2026 Jul–Sep 2025 Jul–Sep 2026 Jan–Sep 2025 Jan–Sep LTM, Oct 2025– Sep 2026 2025 Jan–Dec Income from property management, SEK M 1,126 1,253 3,427 3,474 4,558 4,606 Reversed: Net interest items, SEK M 564 506 1,644 1,556 2,170 2,082 Income from property management excluding net interest, SEK M 1,690 1,759 5,071 5,030 6,728 6,688 Interest coverage ratio, multiple 3.0 3.5 3.1 3.2 3.1 3.2 Surplus ratio 2026 Jul–Sep 2025 Jul–Sep 2026 Jan–Sep 2025 Jan–Sep LTM, Oct 2025– Sep 2026 2025 Jan–Dec Net operating income 1,614 1,702 4,829 4,908 6,444 6,524 Reversed: Coworking income¹ — −118 — −177 −79 −197 Coworking costs¹ — 107 — 165 54 161 Net operating income excluding coworking 1,614 1,691 4,829 4,896 6,419 6,488 Rental income excluding coworking 2,008 2,070 6,202 6,341 8,229 8,426 Service income² 238 219 785 678 1,077 970 Rental and service income excluding coworking 2,246 2,289 6,987 7,019 9,306 9,396 Surplus ratio, % 71.9 73.9 69.1 69.8 69.0 69.1 1. Income and costs respectively, less Group-wide. 2. Jan-Sep 2026 includes non-recurring revenue of SEK 84 M pertaining to reversal of accrued annuity. Net investments, SEK M 2026 Jul–Sep 2025 Jul–Sep 2026 Jan–Sep 2025 Jan–Sep LTM, Oct 2025– Sep 2026 2025 Jan–Dec Acquisitions — 331 — 2,031 54 2,085 Investments in existing properties 985 797 2,953 2,085 4,083 3,215 Total investments 985 1,128 2,953 4,116 4,137 5,300 Divestments −4,839 −453 −10,405 −618 −10,698 −911 Net investments −3,854 675 −7,452 3,498 −6,561 4,389 Proportion of the property value, % −2.9 0.5 −5.4 2.6 −4.8 3.2 30 Sep 2026 30 Sep 2025 31 Dec 2025 Number of shares outstanding, thousands 430,486 492,102 492,102 30 Sep 2026 30 Sep 2025 31 Dec 2025 Net asset value SEK M SEK/share SEK M SEK/share SEK M SEK/share Equity 74,443 172.93 78,663 159.85 78,311 159.14 Reversed: Hybrid bonds −10,161 −23.60 −10,161 −20.65 −10,161 −20.65 Declared, undistributed dividend — — 610 1.24 305 0.62 Derivatives −1,957 −4.55 −948 −1.93 −705 −1.43 Goodwill −3,924 −9.12 −4,247 −8.63 −4,166 −8.47 Deferred tax according to the balance sheet 14,529 33.75 14,974 30.43 15,139 30.76 Net reinstatement value (EPRA NRV) 72,930 169.41 78,891 160.31 78,723 159.97 Less: Estimated fair value, deferred tax −2,586 −6.01 −2,367 −4.81 −2,422 −4.92 Net tangible assets (EPRA NTA) 70,344 163.41 76,524 155.50 76,301 155.05 Reversed: Derivatives according to above 1,957 4.55 948 1.93 705 1.43 Deferred tax in full −11,943 −27.74 −12,607 −25.62 −12,717 −25.84 Net disposal value (EPRA NDV) 60,358 140.21 64,865 131.81 64,289 130.64 27 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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30 Sep 2026 30 Sep 2026 30 Sep 2026 30 Sep 2025 31 Dec 2025 EPRA LTV Group, according to reporting Castellum’s participa- tions in associated companies and JV Total Castellum, including associated companies and JV Total Castellum, including associated companies and JV Total Castellum, including associated companies and JV Interest-bearing liabilities, SEK M 56,287 11,942 68,229 68,513 67,479 Hybrid bonds, SEK M 10,161 — 10,161 10,161 10,161 Currency portion of market value on hedging for loans in foreign currencies, SEK M −1,014 — −1,014 −581 −149 Working capital, net (if liabilities greater than receivables), SEK M 1,854 72 1,926 2,722 2,493 Cash and cash equivalents, SEK M −163 −131 −294 −345 −278 Net liabilities, SEK M 67,125 11,883 79,008 80,470 79,706 Investment properties, SEK M 129,293 23,602 152,895 159,162 158,263 Working capital, net (if receivables greater than liabilities), SEK M — — — 214 — Total assets, SEK M 129,293 23,602 152,895 159,376 158,263 EPRA LTV, % 51.9 50.3 51.7 50.5 50.4 Loan-to-value ratio 30 Sep 2026 30 Sep 2025 31 Dec 2025 Interest-bearing liabilities, SEK M 56,287 57,497 57,019 Cash and cash equivalents, SEK M −163 −137 −120 Net interest-bearing liabilities, SEK M 56,124 57,360 56,899 Total assets, SEK M 150,116 157,240 155,889 Loan-to-value ratio, % 37.4 36.5 36.5 Loan-to-value ratio, Property 30 Sep 2026 30 Sep 2025 31 Dec 2025 Net interest-bearing liabilities, SEK M 56,124 57,360 56,899 Investment properties, SEK M 129,293 137,328 136,919 Loan-to-value ratio, Properties, % 43.4 41.8 41.6 Unencumbered assets ratio 30 Sep 2026 30 Sep 2025 31 Dec 2025 Total assets, SEK M 150,116 157,240 155,889 Less secured assets, SEK M −57,879 −75,121 −68,836 Unencumbered assets, SEK M 92,237 82,119 87,053 Total assets, SEK M 150,116 157,240 155,889 Unencumbered assets ratio, % 61.4 52.2 55.8 Secured debts to total assets ratio, % 30 Sep 2026 30 Sep 2025 31 Dec 2025 Secured debts, SEK M 26,613 23,031 22,093 Total assets, SEK M 150,116 157,240 155,889 Secured debt to total assets ratio, % 17.7 14.6 14.2 Net debt/EBITDA, LTM 30 Sep 2026 30 Sep 2025 31 Dec 2025 Net interest-bearing liabilities, SEK M 56,124 57,360 56,899 Net operating income, SEK M 6,444 6,561 6,524 Central administration expenses, SEK M −173 −240 −264 Operating income, SEK M 6,271 6,322 6,260 Net debt/EBITDA, multiple 8.9 9.1 9.1 Dividend yield 30 Sep 2026 30 Sep 2025 31 Dec 2025 Approved dividend — 2.48 2.48 Share price at end of period 124.25 106.30 106.40 Dividend yield, % — 2.3 2.3 Rental and service income in the like-for-like portfolio 2026 Jul–Sep 2025 Jul–Sep 2026 Jan–Sep 2025 Jan–Sep LTM, Oct 2025– Sep 2026 2025 Jan–Dec Rental and service income 2,246 2,407 6,987 7,196 9,385 9,593 Acquired, sold and development properties −221 −69 −589 −540 −443 −291 Coworking, group eliminations and currency adjustment 0 −34 13 −135 −63 −97 Rental and service income in the like-for-like portfolio, SEK M 2,025 2,304 6,411 6,521 8,879 9,205 28 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Definitions Dividend yield Declared dividend as a percentage of the share price at the end of the period. The key metrics illustrate how much of their investment the shareholders receive back in dividends. Unencumbered assets ratio Total carrying amount of assets that are not pledged as collateral, as a percentage of total assets. This key metric illustrates financial risk. Return on equity Income after tax as a percentage of average equity. This key metric illustrates the capacity for generating earnings on the Group’s equity. Return on equity (excluding hybrid) Income after tax less coupon as interest, as a percent- age of average equity excluding average hybrid capital and tax effect that impacted equity. This key metric illustrates the capacity for generating earnings on the Group’s equity. Loan-to-value ratio Interest-bearing liabilities after deduction for cash and cash equivalents as a percentage of total assets. This key metric illustrates financial risk. Loan-to-value ratio, Property Interest-bearing liabilities after deduction for cash and cash equivalents as a percentage of the properties’ fair value. This key metric illustrates financial risk. EPRA EPS – Earnings Per Share Income from property management adjusted for current tax on income from property management, divided by the average number of shares. The estimate of current tax takes into account factors such as depreciation and reconstruction that are deductible for tax purposes. This key metric is a measurement of earnings generation in the operation, less current tax on income from property management. EPRA NRV – Net Reinstatement Value Equity as recognised adjusted for hybrid bonds, declared and undistributed dividends, carrying amounts of derivatives, goodwill and nominal deferred tax. This key metric describes the total equity that Castellum manages on behalf of its owners. EPRA NTA – Net Tangible Assets Equity as recognised adjusted for hybrid bonds, declared and undistributed dividends, carrying amounts of derivatives and goodwill adjusted for the estimated fair value of deferred tax instead of nominal deferred tax. This key metric corresponds to EPRA NRV , but with the difference that deferred tax is based on estimated fair value. EPRA NDV – Net Disposal Value Equity as recognised adjusted for hybrid bonds, declared and undistributed dividends and goodwill. This key metric illustrates the owners’ share of equity. EPRA LTV – Loan to Value Interest-bearing liabilities with additions for hybrid bonds, adjusted for the currency portion of the market value of hedging for loans in foreign currencies, and less cash and cash equivalents. Negative working capital increases interest-bearing liabilities, whereas positive working capital is added to the value of investment properties. Principal associated companies are included in proportion to the share owned. This key metric illustrates financial risk. Income from property management Income before tax adjusted for change in value of properties, derivatives, financial holdings and goodwill, as well as Castellum’s share of earnings from associ- ated companies and joint ventures excluding income from property management. Income from property management is a measurement of earnings generation in the operation, after financial costs but excluding changes in value. Rental and service income in the like-for-like portfolio Rental and service income from properties that formed part of the portfolio throughout the reporting period and the entire comparative period, adjusted for currency. Development properties, coworking and properties that were acquired or sold are not included. This key metric illustrates the performance of rental and service income excluding non-recurring effects – for example, early vacancies – unaffected by acquired and sold properties. Net investments Net of property acquisitions, investments in the existing property portfolio and property sales. This key metric illustrates the investment volume. Net debt/EBITDA Interest-bearing liabilities, less cash and cash equivalents, at the end of the period in relation to net operating income less central administrative costs over the last 12 months. This key metric illustrates financial risk. Interest coverage ratio Income from property management after reversal of net financial items, as a percentage of net interest items. This key metric illustrates financial risk. Secured debt to total assets ratio Secured debts as a percentage of total assets. This key metric illustrates financial risk. Surplus ratio Net operating income adjusted for coworking and other income, as a percentage of rental income and service income excluding coworking. This key metric clarifies the profitability of the properties. Alternative performance measures Castellum applies the European Securities and Market Authority (ESMA) guidelines on alternative performance measures. According to these guidelines, an alternative performance measure is a financial measurement of historical or future earnings trends, financial position, financial earnings or cash flows that are not identified or indicated in the applicable rules for financial reporting (IFRS® reporting standards and the Swedish Annual Accounts Act). Castellum is also a member of the European Public Real Estate Association (EPRA), which is why the financial key metrics EPRA EPS, EPRA NRV , EPRA NTA, EPRA NDV , EPRA LTV and EPRA vacancy rate are reported. The calculation of key metrics includes balance sheet items reported as Assets held for sale and Liabilities attributable to assets held for sale in accordance with IFRS 5 to ensure comparability and a fair view of the underlying operations. Other key metrics and definitions Number of shares Registered number of shares – the number of shares registered at a given point in time. Number of shares outstanding – the number of shares registered with a deduction for the company’s own repurchased shares at a given point in time. Average number of shares – the weighted average number of shares outstanding during a given period. Return on total capital Income before tax with reversed net interest and changes in values on derivatives over the last 12 months as a percentage of average total capital. Data per share Calculation of income and cash flow per share uses the average number of shares. Calculation of assets, equity and net asset value per share uses the number of shares outstanding. Economic occupancy rate Contractual annual rent excluding discounts on the balance sheet date, as a percentage of rental value excluding development properties on the balance sheet date. EPRA Vacancy rate The estimated market rent for vacant leases divided by the rental value on an annual basis for the entire asset portfolio excluding properties classified as development properties. Property type Castellum’s property types are: office, public sector properties (customers that are directly or indirectly tax funded), warehouse/light industry, retail and development projects and land. The property is categorised on the basis of its primary rental value, even though other categories may exist within the property. Property costs Property costs included costs for operation, maintenance, property tax, and lease and property administration. Rental value Rental and service income with the addition of estimated market rent for vacant spaces. Contract value Rental and service income on an annual basis for Castellum’s leases. SEK per square metre Property-related key metrics, expressed in terms of SEK per square metre, are based on properties owned at the end of the period. Properties acquired/completed during the year have been restated as if they had been owned or completed for the whole year, while properties disposed of have been completely excluded. Development projects and undeveloped land have been excluded. For interim financial statements, the key metrics are reported rolling twelve months. Net leasing Rental and service income for leases signed during the period for the entire property portfolio, less rental income for leases terminated during the period. 29 CASTELLUM INTERIM REPORT JANUARY–SEPTEMBER 2026

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Castellum Aktiebolag (publ) Box 2269, SE-403 14 Gothenburg, Sweden Office address: Lilla Bommen 5c Tel: +46 (0)31-60 74 00 www.castellum.se Domicile: Gothenburg Corporate ID No.: 556475-5550 Contact details For more information please contact: Pål Ahlsén, CEO, telephone +46 (0)76-807 97 02 or Christoffer Strömbäck, CFO, telephone +46 (0)70-249 72 55. About Castellum Castellum is a Swedish property company that owns, manages and develops commercial properties in growth cities. As of 30 Septem- ber 2026, the property value totalled approximately SEK 129 Bn. The company is listed on Nasdaq Stockholm Large Cap and is classified as green under the Green Equity Designation. Castellum is the only Swedish property company included in the Dow Jones Sustainabil- ity Indices (DJSI). Beyond expectations. www.castellum.se Financial calendar Year-end report 2026 12 February 2027 2026 Annual Report, published on the company’s web site 24 March 2027 Interim report January–March 2027 28 April 2027 Annual General Meeting 2027 29 April 2027 Half-year report January–June 2027 15 July 2027 Interim report January–September 2027 21 October 2027 Year-end report 2027 11 February 2028

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Visit Castellum’s web site to download and subscribe to press releases and financial reports. castellum.com Q3 Interim report January– September 2026