Updated

Updated · BleepingComputer · Sep 15

Microsoft Ships 6 Emergency Windows Patches to Fix RDS Failures After September Updates

Updated

Updated · BleepingComputer · Sep 15

Microsoft Ships 6 Emergency Windows Patches to Fix RDS Failures After September Updates

Q: What hidden flaw in the latest Windows patch forced an emergency fix for virtual machines?

The hidden flaw was a **Hyper-V regression in Plan9 host-folder sharing** introduced by the September Windows 11 security updates. It affected **Host Compute Service-managed Linux virtual machines**, where folders shared from the Windows host using Plan9 would either **not appear inside the guest** or become **inaccessible**. Microsoft’s own release notes for the emergency patches say the bug hit applications that rely on **HCS-managed VMs** and **Plan9-based file sharing**. That made it especially disruptive for sandbox-style workloads and tools such as **WSL** and **Claude Cowork**, which depend on those shared mounts to access host files. Evidence from user reports and Microsoft’s known-issues documentation points to the same failure pattern: the VM itself would boot normally, but the **Plan9/virtiofs mount layer broke**, producing errors like missing shares or failed mounts. Standard Hyper-V virtual machines that do not use Plan9 were not broadly affected. Microsoft addressed the issue in the September 14 out-of-band updates for Windows 11, including **KB5129195** for versions 24H2 and 25H2 and **KB5129194** for version 26H1. In short, the emergency fix was forced by a patch-introduced bug that **broke Plan9-based host folder mounts in Hyper-V Linux VMs**.

3 articles · Updated · BleepingComputer · Sep 15

September 14 out-of-band updates target Remote Desktop Services crashes and sign-in failures that followed this month’s Windows security patches, which in some cases left servers and admin tools unresponsive.
Six patches cover Windows 10, Windows 11 and Windows Server versions, replacing temporary Group Policy mitigations and avoiding the need to uninstall September security updates to restore RDP.
Windows Server 2022 and 2025 fixes specifically address RDS breakage tied to KB5122882 and KB5122871, while Windows 11 24H2, 25H2 and 26H1 plus Windows 10 21H2 and 22H2 also received repairs.
The Windows 11 out-of-band releases also fix Hyper-V folder-sharing failures with Linux VMs and some multichannel USB Audio Class 1.0 issues, including 8-channel and 3D audio modes.
Microsoft said one USB Audio Class 1.0 bug remains after the September 8 security update—some devices still fail to start or output sound—and the company is still working on a full fix.