Microsoft has confirmed that the Windows 11 security update KB5089549 is causing installation failures on some systems. Affected devices reportedly fail during the restart phase before rolling back automatically and displaying error code 0x800f0922.
The issue affects Windows 11 versions 24H2 and 25H2. According to Microsoft, the problem appears connected to limited free space inside the EFI System Partition, also known as the ESP.
Microsoft Acknowledges Installation Problems
Microsoft said the update may fail during the restart stage at roughly 35% completion. Systems then reverse the installation process and display messages stating that Windows is undoing changes.
The company explained that devices with very small amounts of free space inside the EFI System Partition are most likely to encounter the issue. Systems with 10 MB or less available space appear especially vulnerable.
Microsoft also noted that affected devices may generate CBS log entries connected to insufficient partition space and failed servicing boot file operations.
Security Update Included Major Changes
KB5089549 was released as part of Microsoft’s May 2026 Patch Tuesday rollout. The update included fixes for more than 120 security vulnerabilities affecting Windows systems.
The package also introduced Secure Boot certificate deployment improvements and created a new SecureBoot folder on supported devices. Microsoft later clarified that the folder is expected behavior and not a security problem.
Some users additionally reported slower internet speeds after installing the update. Microsoft has not officially confirmed a direct link between KB5089549 and network performance issues.
Microsoft Published Temporary Workarounds
Microsoft released temporary mitigation steps while engineers work on a permanent solution. One workaround involves modifying a registry value related to EFI partition padding before attempting the update again.
The company also deployed a Known Issue Rollback mechanism for many consumer and unmanaged business systems. Microsoft said restarting affected devices may help the rollback apply more quickly.
Enterprise administrators can also use a dedicated Group Policy package designed to disable the problematic change temporarily until Microsoft releases a permanent fix.
Users Report Additional Problems
Windows users reported repeated installation failures across Microsoft forums and community platforms shortly after the update launched.
Some users claimed their systems entered rollback loops after failed installation attempts. Others reported temporary boot issues after repeated restart failures during the update process.
Several online reports also mentioned slower internet connectivity on some Windows 11 systems after the update installed successfully. However, those complaints remain largely unconfirmed.
Conclusion
KB5089549 issues are causing installation failures and rollback problems on some Windows 11 systems after Microsoft’s latest Patch Tuesday release. The company has acknowledged the problem and published temporary mitigation steps while preparing a permanent fix.
As Windows updates continue growing more complex, administrators will likely face increasing pressure to monitor system partition configurations and update reliability more closely.
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