X0609 4 2026-10-01 0 0001877939 Castellum, Inc. CTM 0001944338 Bell David T false 1934 OLD GALLOWS ROAD SUITE 350 VIENNA VA 22182 0 1 0 1 Chief Financial Officer Treasurer 0 Common Stock 2026-10-01 4 P 0 1396 0.5352 A 18651 D Pursuant to the terms of the Castellum, Inc. 2025 Employee Stock Purchase Plan, the reporting person purchased 1,396 shares of common stock of the Registrant. The per share purchase price was calculated at a discount of fifteen percent to the closing price of the Registrant's common stock as quoted on the NYSE American LLC on September 30, 2026. /s/ David T. Bell 2026-10-01