Microsoft Confirms KB5089549 Windows 11 Security Update Fails to Install on Some Systems
Microsoft has confirmed that the May 2026 Windows 11 security update KB5089549 fails to install on devices with insufficient EFI System Partition space, triggering 0x800f0922 errors.
Microsoft has confirmed that the May 2026 Windows 11 security update (KB5089549) fails to install on some systems and triggers 0x800f0922 errors. The company acknowledged the issue in a known-issue advisory, stating that affected devices see the update roll back automatically during the reboot phase.
The root cause is insufficient free space on the EFI System Partition (ESP). Microsoft explained that devices with 10 MB or less available space on the ESP are particularly vulnerable. The installation proceeds through initial phases but fails at approximately 35–36% completion during reboot, displaying the message "Something didn't go as planned. Undoing changes."
Affected users impacted by these installation problems may also find log entries pointing to insufficient ESP free space, such as "SpaceCheck: Insufficient free space" and "ServicingBootFiles failed. Error = 0x70." The logs may also indicate that third-party or OEM files outside of Microsoft boot directories are consuming space on the partition.
While Microsoft is still working to resolve this issue, it advised affected customers to mitigate it using the Known Issue Rollback (KIR) feature, which reverses buggy updates pushed via Windows Update. In enterprise-managed environments where IT departments control Windows updates, admins can manually mitigate the problem by installing and configuring a specific Group Policy.
"You will need to install and configure the Group Policy for your version of Windows to resolve this issue," Microsoft said. "You will also need to restart your device(s) to apply the group policy setting. Note that the Group Policy will temporarily disable the change causing this issue."
Microsoft released the KB5089549 cumulative update last week, along with dozens of other bug fixes, security patches, and improvements, including a fix for another known issue that causes some Windows 11 systems to boot into BitLocker recovery after installing the April 2026 Windows security updates.
Earlier this month, Microsoft also addressed a Windows Autopatch bug that caused driver updates restricted by administrative policies to be deployed on some Autopatch-managed Windows devices across the European Union, and confirmed that the April 2026 security updates were causing failures in third-party backup applications using a vulnerable driver.
The KB5089549 installation failure adds to a growing list of Windows update quality issues that have frustrated IT administrators and home users alike. The reliance on the Known Issue Rollback mechanism, while effective, requires manual intervention in enterprise environments, placing an additional burden on IT teams already managing complex patch cycles. Microsoft has not yet announced a timeline for a permanent fix.