Microsoft Fixes Windows 11 Update Failure Affecting Devices with Limited EFI Partition Space (KB5089549)
What Happened – Microsoft identified that the May 2026 Windows 11 security update (KB5089549) could fail with error 0x800f0922 on devices whose EFI System Partition (ESP) had ≤10 MB free space. The update would roll back during the reboot phase, leaving the system in a “Something didn’t go as planned” state. Microsoft released a preview cumulative update (KB5089573) on May 26 2026 that resolves the issue and made the fix available in the June Patch Tuesday roll‑out.
Why It Matters for TPRM –
- Update‑failure can halt security‑patch deployment, extending exposure windows for known vulnerabilities.
- Enterprise‑wide rollout delays may impact compliance calendars and service‑level agreements.
- The root cause is a configuration limitation (ESP size) that many third‑party device‑management tools must account for.
Who Is Affected – Enterprises and managed service providers that deploy Windows 11 (versions 24H2, 25H2) across any industry; particularly environments with automated patching or thin‑client devices with constrained EFI partitions.
Recommended Actions –
- Verify ESP free space ≥10 MB on all Windows 11 endpoints before applying May 2026 updates.
- Deploy the KB5089573 preview cumulative update (or later June Patch Tuesday) to remediate the issue.
- If immediate remediation is not possible, enable the “Known Issue Rollback” Group Policy as a temporary mitigation.
- Update internal patch‑management playbooks to include ESP‑size checks for future releases.
Technical Notes – The failure stems from insufficient free space on the EFI System Partition, causing the update engine to abort during the reboot stage (≈35‑36 % progress). No CVE is associated; the problem is a misconfiguration rather than a vulnerability. Log entries such as “SpaceCheck” and “ServicingBootFiles failed” indicate the condition. Source: BleepingComputer