The bottom line: Windows 11 KB5089549 aborts installation when the EFI System Partition has less than 10 MB free space and can be resolved through Known Issue Rollback or Group Policy configuration.
Microsoft’s May 2026 security update for Windows 11 (KB5089549) cannot be installed on systems with less than 10 MB of free space on the EFI System Partition (ESP) and generates error 0x800f0922. Microsoft confirms the issue and recommends mitigation measures for affected users.
The KB5089549 update typically fails on affected devices during the reboot phase at approximately 35–36% completion. Users see the message “Something didn’t go as planned. Undoing changes.” The cause is insufficient free space on the EFI System Partition, particularly when less than 10 MB is available. Log files contain entries such as “SpaceCheck: Insufficient free space” or “ServicingBootFiles failed. Error = 0x70”.
For affected systems, Microsoft recommends two solution approaches: In consumer environments, the Known Issue Rollback feature can be enabled, which automatically reverts the failed update installation. In enterprise environments with centralized update management, IT administrators can manually deploy and configure a corresponding Group Policy that temporarily disables the problematic change. A restart is required after applying the policy.
Microsoft is still working on a permanent solution but has provided documentation for deploying and configuring Known Issue Rollback policies. Besides resolving this EFI partition issue, the KB5089549 update contains dozens of additional security patches and bug fixes. In a separate known issue, Windows 11 systems may unexpectedly boot into BitLocker recovery after installing the April 2026 security update.
Source: ainews-dev.lumi-systems.io · Published May 18, 2026
Lumi AI News — AI-assisted curation pursuant to Art. 50 EU AI Act. Paraphrase and classification by Lumi News Pipeline v1.5.2.