Take Action: Out-of-band update released to address issues from the September 2026 Windows security update

Microsoft has identified issues that affect some devices after installing the September 2026 Windows security update, released September 8, 2026. On affected devices, host folder shares might be unavailable in Hyper-V-based Linux virtual machines, Remote Desktop Services might stop responding, which can prevent new sessions from being created and can prevent local and remote sign-in, and some USB Audio Class 1.0 devices might fail in multichannel audio modes.    An out-of-band (OOB) update was released today, September 14, 2026, to address these issues. For most versions of Windows, these are cumulative updates that include all improvements from the September 2026 Windows security update released September 8, 2026, so you do not need to install any previous update first, except as noted below for hotpatch updates.    For Windows 11, versions 26H1, 25H2, and 24H2, this OOB update is a security update. It downloads and installs automatically from Windows Update and from Windows Update for Business in accordance with configured policies. It is also available from the Microsoft Update Catalog and syncs automatically with Windows Server Update Services (WSUS).    A corresponding hotpatch update is available from Windows Update for Windows 11, versions 25H2 and 24H2 for devices enrolled in hotpatch updates. Devices must have the September 2026 security update installed to receive this hotpatch update automatically.    The update for Windows 11, versions 26H1, 25H2, and 24H2 includes a security fix to address CVE-2026-62721. The update for Windows 11, version 26H1 also includes a security fix to address CVE-2026-85921. For Windows 11, version 23H2, and Windows 10, version 22H2 (ESU), this update is an optional non-security update. To install it, go to Settings > Windows Update, select Check for updates, and then select Download and install. It is also available from the Microsoft Update Catalog.     For complete guidance and installation instructions, see the relevant KB articles:  Windows 11, version 26H1: KB5129194  Windows 11, versions 25H2 and 24H2: KB5129195  Windows 11, versions 25H2 and 24H2 (hotpatch): KB5129241  Windows 11, version 23H2: KB5129242  Windows Server 2025: KB5129235  Windows Server 2022: KB5129237  Windows 10, version 22H2 and Windows 10 Enterprise LTSC 2021: KB5129236  Windows 10 Enterprise LTSC 2019 and Windows Server 2019: KB5129238  Windows 10 Enterprise LTSB 2016 and Windows Server 2016: KB5129239  Windows Server 2012 R2: KB5129243  Windows Server 2012: KB5129244