On Windows 11, Microsoft has confirmed that the May 2026 Security Update is failing to install on some devices, resulting in error code 0x800f0922. The issue affects systems running versions 24H2 and 25H2 after installing update (KB5089549), released on May 12. According to the company, the failures occur during the reboot phase of the installation process, typically around 35 percent complete.

The problem occurs on devices with limited free space in the EFI System Partition (ESP). Systems with 10MB or less available space are most likely to fail. When the installation breaks, the operating system rolls back the update and displays the familiar recovery "Something didn't go as planned. Undoing changes" error.

In affected devices, users may also find related entries in C:\Windows\Logs\CBS\CBS.log, pointing to insufficient free space on the EFI System Partition. These logs can include messages such as:

• SpaceCheck: Insufficient free space
• ServicingBootFiles failed. Error = 0x70
• SpaceCheck: used by third-party/OEM files outside of Microsoft boot directories

Microsoft already pushed a mitigation

Microsoft says the issue has already been mitigated through Known Issue Rollback (KIR) for consumer and unmanaged business devices. In many cases, simply restarting the computer and checking for updates again may resolve the problem.

For devices managed by an organization, network administrators must manually deploy a Group Policy workaround. However, Microsoft is also offering a direct fix for systems that continue to fail.

How to fix error 0x800f0922 on Windows 11

The company recommends changing a Registry value that reduces the reserved padding Windows 11 uses inside the EFI partition during servicing.

1. Open Start.
2. Search for Command Prompt, right-click the top result, and choose the "Run as administrator" option.
3. Type the following command and press Enter: reg add "HKLM\SYSTEM\CurrentControlSet\Control\Bfsvc" /v EspPaddingPercent /t REG_DWORD /d 0 /f

4. Restart the computer.
5. Open Settings.
6. Click on Windows Update.
7. Click the Check for updates button.

Once you complete the steps, the update KB5089549 should now download and install without issues on Windows 11.

Microsoft says it is working on a permanent resolution that will ship in a future Windows update.

Windows Central's Take

I think most people won't notice this issue because the company has already pushed a fix through Known Issue Rollback. In many cases, restarting the computer and checking for updates again may be enough to install the update normally.

However, this is the kind of problem that can confuse users. The computer may show plenty of free storage space, but the update can still fail due to a hidden system partition running in the background.

The Registry workaround should fix the problem, but I wouldn't recommend that average users rush to edit system settings unless the update keeps failing after multiple attempts. For most people, waiting for the automatic fix is probably the safer option.

I also think this issue shows how Windows 11 updates are becoming more dependent on modern hardware and storage configurations. Older computers and upgraded systems are more likely to encounter these kinds of installation problems.

Have you seen error 0x800f0922 while installing the May 2026 update on Windows 11? Let me know in the comments or take the poll above.

More resources

Explore more in-depth how-to guides, troubleshooting advice, and essential tips to get the most out of Windows 11 and 10. Start browsing here:

• Windows 11 on Windows Central — All you need to know
• Windows 10 on Windows Central — All you need to know

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Mauro Huculak has been a Windows How-To Expert contributor for WindowsCentral.com for nearly a decade and has over 22 years of combined experience in IT and technical writing. He holds various professional certifications from Microsoft, Cisco, VMware, and CompTIA and has been recognized as a Microsoft MVP for many years.