Install error – 0x800f0922 can appear when KB5089549 reaches the restart phase on Windows 11 version 24H2 or 25H2, fails around 35–36%, and Windows undoes the changes. Microsoft tied this specific failure to limited free space on the EFI System Partition. The safest first action is to confirm KB5089549 in Update history, save open work, and install the latest applicable cumulative update that supersedes it. The code alone is not enough to identify this issue.

What KB5089549 error 0x800F0922 means

This guide applies only to the documented failure of the May 12, 2026 cumulative update KB5089549 on Windows 11 versions 24H2 and 25H2. The matching pattern is an installation that proceeds to a restart, stops at approximately 35–36%, rolls back, and may display Something didn’t go as planned. Undoing changes.

According to Microsoft’s KB5089549 release information, the issue especially affects systems whose EFI System Partition has 10 MB or less of free space. This does not mean that every occurrence of 0x800F0922 has the same cause.

Confirm that this is the documented KB5089549 failure

Use the following identity checks before applying the resolution:

  • The device runs Windows 11 version 24H2 or 25H2.
  • Settings > Windows Update > Update history identifies KB5089549 as the failed update.
  • The failure occurs during the restart phase, commonly around 35–36%, followed by Windows undoing the changes.
  • When available, CBS.log contains SpaceCheck: Insufficient free space.
  • When available, CBS.log contains ServicingBootFiles failed. Error = 0x70.

CBS.log may also show a space check involving third-party or OEM files outside Microsoft boot directories. These indicators support the documented EFI System Partition free-space association, but this guide does not provide a procedure for accessing the log or modifying that partition.

If the Windows version, KB number, rollback stage, or log evidence does not match, do not assume that limited EFI space is the cause.

Install the cumulative update that supersedes KB5089549

When this applies: Use this confirmed path when KB5089549 fails with 0x800F0922 on Windows 11 version 24H2 or 25H2.

Prerequisites: The device must be able to receive Windows Update updates, and you must be able to restart it after installation. Save open work before proceeding.

  1. Open Settings > Windows Update > Update history to confirm KB5089549 failed.
  2. Check for updates and install the latest available cumulative update.
  3. If offered, install KB5089573 or any later cumulative update that supersedes it.
  4. Restart when prompted and verify the update completes.

Microsoft’s KB5089573 release information identifies KB5089573 as the first cumulative update that addressed this issue. If Windows Update offers a later applicable cumulative update, install that later update rather than seeking the older preview specifically.

Expected result: The superseding cumulative update installs and remains installed after the restart. Confirm this in Update history.

Risk and rollback: This is a low-risk path with no expected data-loss risk, but it requires a restart. Do not uninstall a successfully installed superseding update unless Microsoft support directs you to do so.

Do not delete, resize, format, mount, assign a drive letter to, or otherwise modify the EFI System Partition as a first-line repair. The supplied Microsoft evidence does not document a consumer procedure for those actions, and an incorrect change can affect startup.

When this is a different 0x800F0922 case

Microsoft’s Windows Update error reference shows why 0x800F0922 should not be identified by code alone. Treat the failure as a different case if it involves another KB, another Windows version, a different installation stage, or different CBS.log evidence.

A changed error code also requires its own diagnostic path. For example, Windows Update error 0x80070005 is an access-denied condition and does not use the KB5089549 recovery path described here.

Generic SFC, DISM, Windows Update troubleshooter, registry, and partition procedures are not confirmed fixes for this exact documented failure and are intentionally excluded.

What to do if the latest cumulative update still fails

  1. Check Update history again and record whether the failed item is the latest applicable cumulative update rather than KB5089549.
  2. Record the Windows 11 version, failed KB number, approximate rollback percentage, exact displayed error, and any relevant CBS.log entries.
  3. Check specifically for SpaceCheck: Insufficient free space and ServicingBootFiles failed. Error = 0x70.
  4. If those entries are absent, stop using the KB5089549 EFI-space diagnosis and escalate the current failure as a separate case with the recorded evidence.

The supplied evidence does not verify one current escalation route for every region or device-management context. It also does not confirm that manual Microsoft Update Catalog installation is required or applicable in every case. Those details must be verified before following a catalog or support procedure; do not select a package or modify the EFI System Partition based on this guide alone.