Microsoft Fixes Windows 11 KB5089549 Install Failures From Limited EFI Space

Microsoft has fixed the known issue that caused installation failures and 0x800f0922 errors when deploying the May 26, 2026, Windows 11 security update KB5089549.

The solution is included in the KB5089573 preview cumulative update released on May 26 and will be available to all users through the June Patch Tuesday updates later this month.

The failures were due to insufficient free space on the EFI System Partition (ESP), which led the update to roll back automatically on affected devices.

What Was Causing KB5089549 Install Failures and How to Fix Them

Microsoft confirmed two weeks ago that the problem affected devices with limited free space on the EFI System Partition, especially those with 10MB or less available. On these systems, the installation process would begin normally but fail during the reboot phase at around 35 to 36 percent completion.

Affected users saw a message stating, “Something didn’t go as planned. Undoing changes,” when the update rolled back. Logs from impacted systems included entries like “SpaceCheck” and “ServicingBootFiles failed,” which pointed to insufficient free space on the EFI System Partition.

Microsoft says the issue has been fixed with updates released on May 26, 2026 (KB5089573) and later. Users who install these updates do not need to use any workaround.

To do so, 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 install issue from occurring.

Microsoft recommends installing the latest update because it includes other improvements and fixes. The same resolution will be rolled out automatically to all users through the June Patch Tuesday cumulative update.

Mitigation Options If You Don’t Install the KB5089573 Optional Update

Users who choose not to install the May 2026 optional update can use Known Issue Rollback (KIR), a Windows feature that undoes problematic updates delivered through Windows Update. KIR is automatically applied to consumer and unmanaged devices.

In enterprise environments, administrators can manually address the issue by installing and configuring the Group Policy provided by Microsoft. Instructions for deploying the Known Issue Rollback group policies are available on Microsoft’s support website.

The preview 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 various 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 failures in third-party backup applications that relied on a vulnerable driver.

The company also fixed a Windows Autopatch bug that led to administrator-restricted driver updates being deployed on some devices managed by Autopatch in the European Union.