Microsoft confirmed May 2026 Windows 11 security update KB5089549 fails to install on some systems triggering 0x800f0922 errors. The known issue affects devices with limited free space on EFI System Partition especially when device has 10 MB or less space available. Installation proceeds through initial phases but fails during reboot phase at approximately 35-36% completion.
Users impacted by installation problems see “Something didn’t go as planned. Undoing changes.” message when installation rolls back. Microsoft stated affected devices may find log entries pointing to insufficient ESP free space causing automatic rollback. The company is rolling out emergency server-side update to address installation errors according to latest announcements.
Microsoft released KB5089549 cumulative update last week along with dozens of other bug fixes, security patches, and improvements. The update includes fix for known issue causing some Windows 11 systems to boot into BitLocker recovery after installing April 2026 security updates. Secure Boot certificates used by most Windows devices are set to expire starting in June 2026 making this update critical.
CloudLinux released rebootless patches for EL8 kernel family within 24 hours while Ubuntu patch status remains needs evaluation. Users can check EFI storage before installing monthly updates by opening PowerShell admin and running Get-Partition script. The update addresses over 120 documented vulnerabilities alongside quality improvements from previous optional preview releases.
Microsoft advised users to apply vendor kernel patches when they become available or disable vulnerable ESP modules through module blacklist as temporary mitigation. Systems with 100MB ESP space believed to be more than enough can run out when firmware updates released by OEMs leave bulky files behind. The update introduces new Secure Boot certificate targeting data increasing coverage of devices eligible to automatically receive new certificates.
