Microsoft confirms Windows 11 May 2026 Security Update KB5089549Released on May 12, failing to install on some devices running versions 24H2 and 25H2. The installation often fails during the reboot process, usually around 35 percent, and displays error code 0x800f0922. In affected systems, the update rolls back and displays a message indicating that the changes are being undone.
The main reason seems to be limited free space in the EFI system partition. Devices with 10 MB or less of available space are most likely to experience this issue.
What Windows 11 KB5089549 installation failures look like
In addition to the rollback message, affected systems may display related entries in C:\Windows\Logs\CBS\CBS.log that point to insufficient free space on the EFI system partition. Examples of these log entries include:
- spacecheck: insufficient free space
- Servicingbootfiles failed. error = 0x70
- spacecheck: used by third-party or OEM files outside Microsoft’s boot directories
These messages indicate that the problem is location related rather than a broader problem with the installation process.
Microsoft’s known issue rollback mitigation and workarounds for persistent errors
AD has implemented a mitigation using known issue rollback (KIR) for consumer and unmanaged business devices. In many cases, simply restarting the computer and checking for updates again will allow the update to install normally without any additional steps.
For devices managed by an organization, network administrators need to manually deploy the Group Policy workaround to apply the mitigation.
For systems that are still experiencing problems after applying KIR mitigations, Microsoft has provided a registry workaround. This reduces the reserved padding that Windows uses inside the EFI partition during servicing.
Editing the registry can be risky and can cause system damage if done incorrectly. It is recommended to backup the entire system before making any changes.
To apply the solution, open the Start menu, search for Command Prompt, right-click on the top result and select Run as administrator.
- Type the given command and press Enter. After that, restart the computer.
- Next, open Settings and navigate to Windows Update.
- Click on check for updates. update
KB5089549 should now download and install successfully after the registry changes are applied.
Permanent Fixes in Development and Other 2026 Windows 11 Update Problems
Microsoft has announced that it is working on a permanent solution to this problem, which will be included in a future Windows update. No specific timeline has been given for when the fix will be released.
This issue is the latest in a series of issues affecting the Windows 11 update in 2026. The April update caused third-party backup software to break due to a weak driver block, and the same month, Windows Server 2025 systems experienced BitLocker recovery prompts and failures during update installation.
Devices with older hardware or advanced system configurations are more affected by these partition and servicing problems.
