Windows 11 update fails install

Microsoft has confirmed that its May 12, 2026 Windows 11 security update, KB5089549, is failing to install on some devices and can end with error 0x800f0922 and an automatic rollback. The company says the issue affects Windows 11 versions 24H2 and 25H2 and is tied to limited free space in the EFI System Partition, or ESP, which stores boot files. On affected machines, the update can appear to install normally at first and then fail during reboot, with Microsoft saying the break point is often around 35% to 36% completion. ### Why is this update failing on some machines? Microsoft’s release-health documentation says the common trigger is an ESP with 10 MB or less of free space. That partition is separate from ordinary disk free space, which means users can have plenty of storage available in Windows and still hit the failure. The visible symptom is often a restart, a failed install, and a message that Windows is undoing changes. (support.microsoft.com) BleepingComputer and The Register reported that Microsoft added the issue to its known-problems documentation days after the patch shipped. Computerworld said administrators and consultants were frustrated because the problem consumes patching time while leaving some systems without the month’s security fixes. (learn.microsoft.com) ### What does 0x800f0922 actually point to here? Error 0x800f0922 is not new in Windows servicing, but in this case Microsoft is linking it to the boot partition constraint rather than a generic download or servicing problem. The company’s release-health page says the update may complete early phases and then fail only when the reboot stage needs to write boot-related changes. That helps explain why the problem can look random to users until the restart phase begins. (bleepingcomputer.com) Microsoft’s own support pages and Q&A responses also point administrators toward ESP-related remediation rather than waiting for repeated retries. The company has not said KB5089549 was recalled. A Microsoft Q&A response says the known issue is associated with low ESP free space and recommends supported mitigation steps. (learn.microsoft.com) ### Where do Secure Boot certificates fit into this? Microsoft has been rolling out Secure Boot certificate updates ahead of the expiration of older certificates beginning in June 2026. Its support guidance says Windows devices are receiving newer 2023 certificates through Windows-managed updates, and that some devices may also require OEM firmware support for the process to complete correctly. (learn.microsoft.com) Neowin and other outlets tied KB5089549 to that broader Secure Boot servicing effort. Microsoft’s Secure Boot troubleshooting guide says certificate servicing depends on a scheduled task and a staged process between Windows and UEFI firmware, which helps explain why boot-partition space and boot-trust updates are showing up in the same troubleshooting path. Microsoft has not publicly said the certificate rollout is the sole cause of every KB5089549 failure, but its documentation shows the two processes are operationally connected. (support.microsoft.com) ### Why are administrators paying attention to the partition layout? Microsoft says the ESP’s minimum size is managed by the operating system, but the current issue shows that older or tighter layouts can leave too little working room for a modern security update. The Register reported that devices with constrained boot partitions are especially exposed to this month’s failure mode, and Microsoft’s own documentation now gives that threshold as 10 MB or less free. (neowin.net) A separate Microsoft Q&A thread from earlier this year described Windows 11 upgrade failures on systems with a 100 MB EFI partition, suggesting that partition sizing has already been a practical limit for some upgrade paths. That thread does not address KB5089549 directly, but it shows the ESP size issue predates this month’s patch. (theregister.com) ### What should users and IT teams watch next? Microsoft’s KB5089549 support page says the update remains the May 12 cumulative security release for Windows 11 24H2 and 25H2, and the company directs users to the Windows release-health dashboard for the latest status. Microsoft’s Secure Boot guidance also says the older certificates begin expiring in June 2026, making the next several weeks important for administrators tracking both monthly patching and trust-store updates. (learn.microsoft.com) (support.microsoft.com)