Microsoft Confirms September 2026 Windows 11 Update Caused Compatibility Failures

Microsoft has confirmed that a cumulative update for Windows 11 released in September 2026 caused functional abnormalities for some users. The update, a monthly release for Windows 11, was intended to fix security vulnerabilities, improve system stability and introduce some feature improvements. After it was released, a large number of users reported compatibility and functionality problems, and Microsoft subsequently publicly confirmed the failures. The affected functions have been confirmed to involve multiple system components.

Some users found that after the update was installed, certain functions no longer worked properly, some settings options behaved abnormally, and individual built-in apps ran unstably, responded slowly or failed to launch. Other users reported problems related to the taskbar, the Start menu and some system services. Microsoft said it has recorded these known issues through its health status page and has begun investigating the causes. Microsoft said preliminary analysis suggests the abnormalities are related to compatibility changes among some system components after the update, and the specific root cause is still being further confirmed.

To mitigate the impact, Microsoft has used its Known Issue Rollback mechanism to address some of the failures. This mechanism allows Microsoft to remotely disable the specific code paths causing the problems without requiring users to fully uninstall the update, thereby restoring the normal operation of the affected functions. Microsoft noted that the update also patched multiple security vulnerabilities. For users already affected, Microsoft is gradually resolving the failures through subsequent updates and emergency fixes.

Microsoft is still continuously collecting user feedback and developing additional fixes. Microsoft said the fixes will address the compatibility and stability problems caused by the September 2026 update.