Microsoft has released an emergency out-of-band update to fix bugs introduced by its record-breaking September Patch Tuesday release, which had patched nearly 1,000 vulnerabilities in the company's largest update to date. The fixes address issues affecting businesses, developers and gamers, underlining how increasingly frequent these emergency patches have become as Microsoft grapples with quality problems in its regular update cycle.

The September update had caused problems with folder shares on Hyper-V-based Linux virtual machines, Remote Desktop Services sessions, and certain USB audio devices. The new out-of-band update, issued the day before this report, covers Windows 11 versions 26H1, 25H2 and 24H2, as well as Windows Server 2025 and 2022, LTSC versions of Windows 10, and Windows Server 2012 and 2012 R2. Such emergency updates were once rare but have become common in 2026, with Microsoft issuing four in January after a buggy Windows 11 patch, two more in March over installation failures and account sign-in problems, and another in July to fix an Intel driver issue causing performance and battery problems.