MICROSOFT’S September 2026 security update KB5124008 for Windows 11 24H2 and 25H2 has caused several confirmed functional problems. Microsoft says some USB Audio Class 1.0 devices may fail to start or produce sound, showing “This device cannot start (Code 10)” in Device Manager. Volume controls may stop working and the sound settings page may become unresponsive.
Devices that work in stereo may lose audio when switched to multichannel, eight-channel or 3D modes; Microsoft’s interim advice is to use two-channel mode.
Microsoft has also reported instability in Remote Desktop Services on some enterprise devices, including connection failures, login anomalies, lengthy waits on the “configuring remote desktop” screen, and unresponsive File Explorer or management tools. Linux virtual machines using Hyper-V’s Plan9 sharing mechanism may also be unable to access host folders, affecting some HCS-based VM management applications, including Claude Cowork.
Separately, users have reported File Explorer crashes, post-login black screens, File History failing to detect backup drives and AMD graphics driver timeouts, but these reports have not been confirmed by Microsoft. The article says uninstalling KB5124008 resolves the reported problems, although doing so removes a security update that fixes multiple flaws and could increase exposure. Microsoft is collecting feedback and working on a fix.