Microsoft has started rolling out an emergency out-of-band update to fix problems with its record-breaking September patch Tuesday update. The software giant patched nearly 1,000 flaws in its biggest update ever this month, but it also introduced some bugs that have affected businesses, developers, and gamers.

The September patch Tuesday affected folder shares on Hyper-V-based Linux virtual machines, Remote Desktop Services sessions, and some USB audio devices. Microsoft’s out-of-band update, released yesterday, addresses these issues across Windows 11 versions 26h1, 25H2, and 24H2. Microsoft has also released updates for Windows Server 2025 and 2022, the LTSC versions of Windows 10, and Windows Server 2012 and Windows Server 2012 R2.

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.