Microsoft has officially confirmed a new issue affecting the May 2026 cumulative update for Windows 11, with some users unable to install the update due to error code 0x800f0922. The problem impacts systems running Windows 11 versions 24H2 and 25H2, where the update fails during reboot and automatically rolls back the installation.
Windows 11 KB5089549 Installation Failure Explained
The affected update is KB5089549, released as part of Microsoft’s May 2026 Patch Tuesday rollout. According to Microsoft, the update installs normally at first, but fails during the restart phase at around 35–36% completion. Windows then removes the update and displays the message:
“Something didn’t go as planned. Undoing changes.”
Users are then shown the 0x800f0922 error code.
What Is Causing Error 0x800f0922?
Microsoft says the issue is linked to devices with very limited free space on the EFI System Partition (ESP). Systems with 10 MB or less of free space in the EFI partition are most likely to experience the installation failure.
Affected systems may also generate log entries such as:
- “SpaceCheck: Insufficient free space”
- “ServicingBootFiles failed. Error = 0x70”
These errors indicate the update cannot complete Secure Boot servicing operations because the EFI partition lacks enough storage space.
Microsoft’s Current Workaround
Microsoft has already published a temporary workaround while it prepares a permanent fix. Advanced users and IT administrators can modify a registry value to reduce EFI partition padding requirements and retry the update.
The workaround involves running this command in an elevated Command Prompt:
reg add "HKLM\SYSTEM\CurrentControlSet\Control\Bfsvc" /v EspPaddingPercent /t REG_DWORD /d 0 /fAfter restarting the PC, users can try installing the update again. However, Microsoft warns that editing the registry incorrectly can cause system problems, so creating a backup first is strongly recommended.
Microsoft Is Rolling Out a Fix
Microsoft says it has already deployed a Known Issue Rollback (KIR) for some consumer and unmanaged enterprise systems. In many cases, simply restarting the computer and checking for updates again may resolve the issue automatically.
A more permanent fix is expected in a future Windows 11 update.
Should You Be Worried?
Most Windows 11 PCs are not affected by the issue. The problem appears limited to systems with unusually small or nearly full EFI partitions, which are more common on older installations, upgraded systems, or PCs with customized OEM partitions.
If your device installed the May 2026 update successfully, no action is needed.
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