Microsoft rolled out an emergency out-of-band update across Windows 11 versions and server editions to repair multiple regressions introduced by its September 2026 Patch Tuesday release, which had addressed a record 966 flaws, including two actively exploited zero-day vulnerabilities, across Microsoft products when it was released last week on Sept. 8.
Emergency Patches Target Remote Desktop, Virtualization, and Audio Failures
Just one week after pushing out its largest update in history, Microsoft was forced to reverse course and deploy emergency out-of-band patches to address severe regressions that impacted businesses, developers, and gamers alike. The corrective releases—designated as KB5129195 for Windows 11 24H2 and 25H2, taking them to builds 26100.9457 and 26200.9457, and KB5129194 for Windows 11 version 26H1—arrived to undo systemic instability caused by the September deployment. Microsoft also released updates for Windows Server 2025 and 2022, the LTSC versions of Windows 10, and Windows Server 2012 and Windows Server 2012 R2. Eligible 24H2 and 25H2 machines can apply a “hotpatch” without a restart.
Among the primary targets of the emergency patches were Remote Desktop Services, which Microsoft says could turn unstable and cause connection or sign-in failures. According to technical reports, the initial September update also caused the Microsoft Management Console, RDS Licensing Diagnoser, File Explorer, and even the Windows Update page to stop responding. The update also closes a privilege escalation flaw that September’s patch hadn’t fully fixed, specifically addressing an elevation of privilege flaw in the User-Mode Power Service after the first one apparently didn’t fully close it. On 26H1, it additionally patches a Secure Kernel Mode elevation bug.
Hyper-V Linux Shares and Audio Hardware Partially Restored
Developers relying on virtualization tools experienced immediate friction after the September deployment. There’s also a Hyper-V fix for apps that couldn’t reach host folders shared with Linux VMs over Plan9, which is what had been breaking Claude Cowork on Windows. Its workspace lost access to local files, and Anthropic added an in-app error message that blamed the Windows update.
Audio hardware also suffered collateral damage. Multichannel audio on some USB Audio Class 1.0 devices works again too, restoring 8-channel and 3D modes on some USB audio devices that still worked in plain stereo. However, this audio fix only goes part of the way. Microsoft still lists a known issue in which some devices fail to start in Device Manager, produce no sound, or show volume controls stuck at zero, throwing a Code 10 error. Microsoft says only that it is working on a resolution.
Unresolved Radeon GPU Crashes and Enterprise Explorer Freezes
Despite deploying the mandatory cumulative emergency packages, Microsoft left several prominent bugs off the changelog. What isn’t fixed is probably the part PC gamers care about. Radeon owners have been reporting driver timeouts, black screens, vanishing displays and full system freezes since KB5124008 landed, sometimes returning right after a clean driver reinstall. Reports seem to span a wide range of cards, from the RX 6600 up to the RX 9070 XT, and Microsoft still hasn’t acknowledged it as a known issue.
Moreover, explorer.exe crashes and File History failing to detect external drives are also still open. The emergency fix arrives as KB5129195 for Windows 11 24H2 and 25H2 as a mandatory cumulative update that installs automatically, so users who skipped the big September 8 release (KB5124008) will get its changes as well. Microsoft also shipped matching packages for Windows 11 26H1 and 23H2, Windows 10 21H2 and 22H2, and several Windows Server and LTSC releases.
Record Vulnerability Patching Strains Update Stability
The sheer scale of the September Patch Tuesday cycle highlights the extensive nature of the update. The software giant patched nearly 1,000 flaws in its biggest update ever this month, addressing a record 966 flaws including two actively exploited zero-day vulnerabilities. The two zero-day exploits that were addressed last week include CVE-2026-81963 and CVE-2026-85880. The former was a flaw in the Windows Update Stack and allowed an attacker to gain System privileges, while the latter was a Windows Advanced Local Procedure Call (ALPC) vulnerability that also allowed attacks to gain System privileges.
In the past it was unusual for Microsoft to issue out-of-band updates to Windows, but it has become far more common this year. In January, the company was forced to issue four out-of-band updates after a buggy Windows 11 patch. In March, the company then had to issue two emergency updates because of installation failures and Microsoft account sign-in problems. Microsoft also released an out-of-band update in July to address an Intel driver issue that was causing performance issues and battery drain. Cybersecurity experts previously told Mashable back in April that AI has been a factor in the discovery of bugs and exploits, for good and bad, which is why new operating system updates have had so many fixes in each new patch. At the time, Microsoft denied AI playing a role in its most recent update, though in July, Microsoft said that AI-assisted vulnerability discovery would lead to more security fixes in its releases.