Windows 11 update KB5089549 causes installation errors due to low EFI partition space

Per Bleeping Computer, Microsoft has confirmed that the May 2026 Windows 11 security update, identified as KB5089549, is failing to install on certain systems and is triggering 0x800f0922 errors. This known issue is specifically linked to insufficient free space on the EFI System Partition (ESP).

The installation failure occurs when the EFI System Partition has 10 MB or less of available space. During the update process, installations may appear to progress initially but fail during the reboot phase, typically around 35-36% completion, rolling back changes with a "Something didn't go as planned" message. Log entries may indicate "SpaceCheck: Insufficient free space" or "ServicingBootFiles failed. Error = 0x70."

Microsoft is working on a permanent fix and advises affected users to utilize the Known Issue Rollback feature. For enterprise environments, IT administrators can manually mitigate the issue by installing and configuring a specific Group Policy, which temporarily disables the change causing the problem. This update also addresses a separate issue that caused some Windows 11 systems to boot into BitLocker recovery after April 2026 updates.

Source: Bleeping Computer