Microsoft’s August 2026 Patch Tuesday release addresses 421 reported vulnerabilities across Windows, Office, Azure, SharePoint Server, Exchange Server, Defender, and various development products. The broader Microsoft Security Update Guide count nevertheless shows that August is another unusually large patching month. Windows 11 versions 24H2 and 25H2 receive the fixes through KB5121003. The cumulative update advances Windows 11 24H2 to build 26100.9168 and Windows 11 25H2 to build 26200.9168. Eligible Windows 10 systems enrolled in Extended Security Updates continue to receive security fixes, with KB5120249 applying to Windows 10 21H2 ESU installations.