microsoft has fixed the known issue that caused installation failures and errors 0x800f0922 when deploying the Windows 11 May 26, 2026 security update. KB5089549.
The solution is included in KB5089573 Preview of the cumulative update released on May 26 and will be available to all users via June Patch Tuesday updates later this month.
The failures were due to a lack of free space on the EFI system partition (ESP), which caused the update to automatically roll back on affected devices.
What was causing the KB5089549 installation failures and how to fix them?
Microsoft confirmed two weeks ago that the issue affected devices with limited free space on the EFI system partition, especially those with 10 MB or less available. On these systems, the installation process would begin normally but would fail during the reboot phase when it was 35 to 36 percent complete.
Affected users saw a message saying, “Something didn’t go as planned. Undo changes,” when the update was rolled back. The logs of the affected systems included entries such as “SpaceCheck” and “ServicingBootFiles failed”, which indicated that there was not enough free space on the EFI system partition.
Microsoft says the issue was fixed with updates released on May 26, 2026 (KB5089573) and later. Users installing these updates do not need to use any workarounds.
To do this, open Settings, then Windows Update, go to Advanced Options, and select Optional Updates. From there, install KB5089573 or a later update. This will prevent the EFI partition installation issue from occurring.
Microsoft recommends installing the latest update because it includes other improvements and fixes. The same resolution will be automatically rolled out to all users via the June Patch Tuesday cumulative update.
Mitigation options if you do not install the optional update KB5089573
Users who choose not to install the optional May 2026 update can use Known Issues Rollback (KIR), a Windows feature that rolls back problematic updates delivered through Windows Update. KIR is automatically applied to consumer and unmanaged devices.
In enterprise environments, administrators can fix the issue manually by installing and configuring the Group Policy provided by Microsoft. Instructions for implementing known issues rollback group policies are available on the Microsoft support website.
The preliminary cumulative update KB5089573 for Windows 11 versions 24H2 and 25H2 was released on May 26. It includes 30 changes, such as the low latency profile performance feature and several reliability improvements.
This update comes after a series of issues with Windows updates in 2026. Earlier this month, Microsoft confirmed that security updates released in April 2026 caused crashes in third-party backup apps that relied on a vulnerable driver.
The company also fixed a Windows Autopatch bug that caused administrator-restricted driver updates to be deployed to some Autopatch-managed devices in the European Union.
