Windows 11 May 2026 Security Update (KB5089549) Fails to Install on Devices with Limited EFI Partition Space
What Happened — Microsoft confirmed that the May 2026 cumulative update KB5089549 for Windows 11 aborts on systems where the EFI System Partition (ESP) has 10 MB or less free space, returning 0x800f0922 errors and automatically rolling back at ~35 % progress.
Why It Matters for TPRM —
- Update failures can leave endpoints unpatched, exposing them to known CVEs until remediation.
- Enterprise‑managed fleets may experience widespread service disruption during scheduled maintenance windows.
- Mis‑sized ESP partitions are a configuration risk that can be inherited from OEM images or third‑party imaging tools.
Who Is Affected — All industries that deploy Windows 11 on desktops/laptops, with particular impact on enterprise IT environments, MSPs, and OEM‑partner devices.
Recommended Actions —
- Deploy Microsoft’s “Known Issue Rollback” feature or the referenced Group Policy to halt the faulty update.
- Verify ESP free space > 10 MB on all managed devices; enlarge the partition where needed.
- Adjust imaging and provisioning scripts to allocate sufficient ESP capacity for future updates.
- Monitor Windows Update logs for 0x800f0922 errors and confirm successful remediation.
Technical Notes — The failure is triggered by a misconfiguration (insufficient free space on the EFI System Partition). No exploit or malicious code is involved, but the rollback leaves systems vulnerable to any security issues addressed by the update. Error messages include “SpaceCheck: Insufficient free space” and “ServicingBootFiles failed. Error = 0x70”. Microsoft recommends applying a specific Group Policy to temporarily disable the change causing the issue while a permanent fix is prepared. Source: BleepingComputer