Microsoft Windows 11 May Security Update Fails Due to EFI Partition Space Issues
Severity: Medium (Score: 58.5)
Sources: Theregister, Scworld, Feeds.4Sysops, Bleepingcomputer, www.wiz.io
Published: · Updated:
Keywords: microsoft, windows, install, confirms, security, update, issues
Severity indicators: issue
Summary
Microsoft's May 2026 security update (KB5089549) for Windows 11 is failing to install on devices with insufficient free space on the EFI System Partition (ESP), particularly those with 10 MB or less. The installation process proceeds initially but fails during reboot at 35-36% completion, resulting in a rollback and the message, 'Something didn't go as planned. Undoing changes.' The issue is confirmed to trigger error code 0x800f0922. Affected users may find log entries indicating insufficient ESP space. Microsoft has provided workarounds, including a registry modification and a Known Issue Rollback (KIR) for enterprise environments. The update includes numerous security patches for critical vulnerabilities. This situation raises concerns about the reliability of the update process and the trust of IT teams in Microsoft's orchestration and validation logic. Key Points: • The May 2026 Windows 11 security update fails on devices with limited EFI partition space. • Affected systems show error code 0x800f0922 and rollback messages during installation. • Microsoft recommends registry edits and Known Issue Rollback as workarounds.
Detailed Analysis
**Impact** Windows 11 devices with 10 MB or less free space on the EFI System Partition (ESP) are affected, causing the May 2026 security update (KB5089549) to fail installation and roll back. This leaves systems unpatched and exposed to dozens of critical vulnerabilities addressed by the update. The issue impacts both consumer and enterprise environments globally, resulting in delayed patching, increased help desk tickets, and operational disruptions due to failed maintenance windows. **Technical Details** The update failure occurs during the reboot phase at approximately 35–36% completion, triggered by insufficient free space on the ESP. The error code 0x800f0922 is logged, with installation rollback displaying the message "Something didn't go as planned. Undoing changes." No malware, CVEs exploited, or attack infrastructure are involved; this is a system update failure related to partition space management and update orchestration. **Recommended Response** Defenders should apply the Known Issue Rollback (KIR) Group Policy to temporarily disable the problematic update and prevent installation failures. For affected devices, increasing the ESP size to at least 1.5 GB is recommended to ensure update success and Windows Recovery Environment functionality. Registry modifications offered by Microsoft can be tested cautiously in pilot environments before broader deployment. Monitoring update logs for 0x800f0922 errors and rollback messages is advised until a permanent fix is released.
Source articles (10)
- Microsoft confirms Windows 11 KB5089549 fails install, shares workarounds — Neowin · 2026-05-16
Microsoft is currently trying to win back Windows 11 fans by improving the performance of the OS with its "low latency" features that are beginning to roll out. There are still major issues that can p… - Microsoft confirms Windows 11 security update install issues — Bleepingcomputer · 2026-05-18
Microsoft has confirmed that the May 2026 Windows 11 security update ( KB5089549 ) fails to install on some systems and triggers 0x800f0922 errors. This known issue is caused by insufficient free spac… - Windows boot partition runs out of space for Microsoft's May security update — Theregister · 2026-05-18
Microsoft has admitted that the May 2026 security update might fail to install with a "Something didn't go as planned. Undoing changes" message. The problem is related to the EFI System Partition (ESP… - Microsoft May security patch fails for some due to boot partition size glitch — Csoonline · 2026-05-18
“Something didn’t go as planned. Undoing changes.” That’s all the clue some Windows 11 users will get when Microsoft’s May Security Update fails to install because of insufficient free space on the EF… - Windows 11 update KB5089549 causes installation errors due to low EFI partition space — Scworld · 2026-05-18
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… - Microsoft resolves Windows 11 update installation failures caused by partition limits — Feeds.4Sysops · 2026-05-31
Microsoft has released a fix for a persistent bug that prevented the installation of the May 2024 Patch Tuesday update, KB5089549. This issue primarily affected Windows 11 versions 24H2 and 25H2, caus… - Microsoft fixes KB5089549 Windows security update install issues — Bleepingcomputer · 2026-06-01
Microsoft has resolved a known issue causing installation failures and 0x800f0922 errors when deploying the May 2026 Windows 11 security update ( KB5089549 ). As Microsoft explained when it acknowledg… - Microsoft resolves Windows 11 installation error 0x800f0922 caused by small EFI partitions — Feeds.4Sysops · 2026-06-01
Microsoft has addressed a persistent issue that caused the May 2026 security update, KB5089549, to fail on various Windows 11 devices. The problem specifically affected systems where the EFI System Pa… - Microsoft resolves Windows 11 update installation errors | brief — Scworld · 2026-06-01
As detailed in Bleeping Computer, Microsoft has addressed a persistent issue causing installation failures and specific error codes when deploying the May 2026 Windows 11 security update, KB5089549. T… - The Technical Guide To Secure Vibe Coding — www.wiz.io · 2026-06-09
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Timeline
- 2026-05-11 — Microsoft releases May 2026 security update KB5089549: The update includes numerous security patches but begins to show installation issues on some systems.
- 2026-05-16 — Microsoft confirms installation issues with KB5089549: The company acknowledges that the update fails due to insufficient space on the EFI System Partition.
- 2026-05-18 — Microsoft advises on workarounds for installation failures: Users are advised to apply registry edits or Known Issue Rollback to mitigate the installation problems.
- 2026-05-18 — Error code 0x800f0922 reported widely: Users experiencing the installation failure report error code 0x800f0922 in system logs.
Related entities
- Microsoft (Company)
- advisory.it (Domain)
- said.as (Domain)
- T1112 - Modify Registry (Mitre Attack)
- BitLocker (Platform)
- Group Policy (Platform)
- Windows (Platform)