Microsoft has confirmed a known issue with the May 2026 Windows 11 security update (KB5089549) that causes installation failures with 0x800f0922 errors. The root cause is insufficient free space on the EFI System Partition (ESP), particularly on devices with 10 MB or less available. Affected systems fail during the reboot phase at around 35–36% completion and automatically roll back. Microsoft recommends using the Known Issue Rollback feature for consumer devices, while enterprise admins can deploy a specific Group Policy to mitigate the issue until a permanent fix is released.
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