Microsoft ships emergency OOB updates: September security patches break RDS, Hyper-V, and USB audio
Microsoft on 14 Sep shipped emergency OOB updates KB5129194/5129195/5129236/5129235/5129237, fixing RDS instability, broken Hyper-V shared folders with Linux VMs, and silent USB Audio Class 1.0 multichannel devices introduced by the 8 Sep security updates.
Microsoft on 14 Sep 2026 shipped emergency out-of-band (OOB) updates to fix severe regressions introduced by the 8 Sep security updates (KB5122871, KB5122882, and others): Remote Desktop Services (RDS) instability, broken shared folders between Hyper-V and Linux VMs, and silent USB Audio Class 1.0 devices in multichannel mode. RDP connection failures and servers stuck on the "Please wait for the Remote Desktop Configuration" screen are known issues from this wave.
Incident overview
Shortly after the September security updates rolled out, large numbers of admins reported RDS failures. Microsoft confirmed the issues span Windows 11 26H1, 25H2, 24H2, 23H2, Windows 10 22H2 on Extended Security Updates (ESU), Windows Server 2022 and 2025, and Windows Server 2012 nearing end of ESU. OOB updates shipped 14 Sep:
- KB5129194: Windows 11 26H1, build 28000.2956
- KB5129195: Windows 11 24H2 / 25H2, builds 26100.9457 / 26200.9457, cumulative
- KB5129236: Windows 10 21H2 / 22H2
- KB5129235: Windows Server 2025, fixes the RDS failure introduced by KB5122871
- KB5129237: Windows Server 2022, fixes the RDS failure introduced by KB5122882
- KB5129241: Windows 11 25H2 / 24H2 devices enrolled in the hotpatch program that already have the September security updates
Symptoms and impact
Remote Desktop Services
RDS became unstable after the September security updates: new remote sessions may fail, logons drop, some servers hang on the "Please wait for the Remote Desktop Configuration" screen and stop responding. If a VM is no longer reachable via RDP, stop (deallocate) it and restart to restore connectivity temporarily.
Hyper-V, USB audio, and Excel
Apps that host VMs via Host Compute Service (HCS) fail when sharing Windows host directories to Linux VMs over Plan9; shared folders do not appear or are inaccessible in the guest. Some USB Audio Class 1.0 devices fail in multichannel mode (8-channel, 3D audio). This OOB wave fixes the multichannel case but not all audio issues—some device drivers still fail to start, Device Manager reports "This device cannot start. (Code 10)". Separately, the update that patched an Excel remote code execution vulnerability caused paste operations to fail silently with no prompt.
Remediation
- Install the matching OOB update per SKU. Prioritize KB5129235 and KB5129237 on servers.
- Do not uninstall the September security updates to restore Remote Desktop. Uninstalling restores RDS but also removes all September security fixes, including two privilege-escalation zero-days exploited in the wild (CVE-2026-85880 ALPC and CVE-2026-81963 update stack) and a CVSS 9.8 Windows DNS Server remote code execution vulnerability. Cost exceeds benefit.
- Until OOB updates are in place, apply the Group Policy mitigations Microsoft previously published. Switch USB Audio Class 1.0 devices to stereo to restore audio.
- Check endpoints that already auto-updated for Excel paste failures. Keep a small canary and a fast rollback plan for critical servers.
Sources
- Zero Day News: Microsoft releases emergency Windows updates to fix RDS failures
- Pureinfotech: KB5129195 September 2026 OOB updates
- The Register: Microsoft patches Windows and Excel – breaks audio, remote access, and paste