KB5124008 is a Microsoft update from Patch Tuesday September 2026, released on 8 Sep 2026. According to the Security Update Guide it fixes 607 vulnerabilities (Windows). Affected according to our entries: Microsoft Windows 11, Version 26H2, Microsoft Windows 11 23H2, 24H2, 25H2, 26H1 and Windows 10 ESU, Microsoft Windows 11. Known issues with this update: 2 with workaround, 3 fixed.
Some USB Audio Class 1.0 devices might fail to start or produce no audio after installing Windows 11, version 26H2. Microsoft lists the same issue for other Windows client and server versions, where it originates from the September 8, 2026 security updates. For 26H2 the vendor status is Mitigated and a fix in a future Windows update is still being worked on.
Microsoft · Windows 11, Version 26H2
File History is reported to show a false 'Reconnect your drive' message after the 8 Sep 2026 update, and backups stop working. This is reported by users, not yet confirmed by the vendor. A fix is reported to be available with KB5124010, but one report says part of the problem persists.
Microsoft · Windows 11 23H2, 24H2, 25H2, 26H1 and Windows 10 ESU
Always On VPN profiles with automatic protocol selection or fallback (IKEv2 and SSTP) failed after the September 2026 Windows 11 updates. According to secondary sources and research notes, the optional preview update KB5127936 (28 Oct 2026) fixes this. We could not read the vendor page ourselves, so the details are not yet confirmed by a vendor source here.
Microsoft · Windows 11
After installing Windows 11 version 26H2, Credential Guard protected machine accounts may lose their secure channel to an on-premises Active Directory domain. The cause is Machine Identity Isolation (MII), which Windows now honours; it is only supported with Windows Server 2025 domain controllers at Domain Functional Level 2025 or above. Microsoft has resolved the issue with updates released on 2026-09-22 and later.
Microsoft · Windows 11, Version 26H2
The October 2026 Windows security update was released on 2026-10-13 for all supported Windows versions. For Windows 11, version 26H2, it fixes several known problems: Always On VPN, a black screen in Azure Virtual Desktop with FSLogix, and tiered Storage Spaces Direct virtual disks. A limited number of devices may need one additional restart during installation because of the Secure Boot certificate update.
Microsoft · Windows 11
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We check whether your systems are affected, apply workarounds properly and plan for dated changes in good time.
