Windows Update Broke Things? Microsoft Just Rushed Out a Fix
Microsoft released emergency fixes on Sept. 14 for problems caused by its large September Windows update. That September update fixed nearly 1,000 flaws and was described as the company's biggest update ever. Reporting on the fix was published on Sept. 15. The Verge
The faulty update affected businesses, developers and gamers. Three separate problems were involved. Shared folders stopped working on Hyper-V-based Linux virtual machines, which is Microsoft's way of running Linux inside Windows. Sessions using Remote Desktop Services, which lets a person log into another Windows computer over a network, were affected. Some USB audio devices, such as headsets, were affected. The Verge
The fix covers many systems. For PCs, it addresses Windows 11 versions 26H1, 25H2 and 24H2. Related out-of-band updates were released for Windows Server 2025 and 2022. Related updates were also released for the LTSC versions of Windows 10, the long-life versions that avoid frequent change, and for Windows Server 2012 and Windows Server 2012 R2. The Verge
Two downloads define the Windows 11 fix. KB5129195 was released on Sept. 14, 2026 for Windows 11 versions 24H2 and 25H2, covering OS Build 26200.9457. KB5129194 was released on Sept. 14, 2026 for Windows 11 version 26H1, covering OS Build 28000.2956. Microsoft Support
Both packages list the same Hyper-V correction. KB5129195 fixed a Hyper-V known issue where applications using HCS-managed virtual machines had trouble sharing host folders with Linux. KB5129194 fixed the same HCS-managed virtual machine issue for 26H1 systems sharing host folders with Linux.
The known issue was documented on Sept. 11, 2026. Microsoft added 'Host folder shares might be unavailable in Hyper-V-based Linux VMs' to KB5124008 for Windows 11 24H2 and 25H2 on that date. It added the same entry to KB5124012 for Windows 11 26H1 on that date. The support notes for KB5124008 and KB5124012 were originally published on Sept. 8, 2026.
Server servicing is moving in parallel. Microsoft released out-of-band update KB5129235 on Sept. 14, 2026 for Windows Server 2025. The Windows message center published a notice titled 'Take Action: Out-of-band update released to address issues from the September 2026 Windows security update.' The Windows release health hub notes that ACL hardening, a planned security tightening, begins in October 2026.
The broader context here is size and timing. One monthly package with almost 1,000 fixes is like doing plumbing, electrical and roof work on a house in one day. Out-of-band updates handle the exceptions. They ship small, targeted fixes without waiting for the next monthly cycle.
Looking at what this means in practice, some fixes matter more than others. Shared folders and remote logins can stop work completely. Sound problems are annoying but rarely stop builds or logins. In my view, that argues for fixing virtual machines and remote-login computers first, then testing the PC fix before sending it to everyone. Older LTSC and Server systems need the same order, during planned downtime.
Worth flagging for October is what comes next. An emergency fix in September followed by more security work in October rewards good backups and careful testing. Shops that test on a few machines first will have an easier time. The long arc of Windows servicing favors recoverability. Fast correction beats perfect release.
