Microsoft Fixes Windows 11 Boot Failure Bug

Microsoft has fixed a bug in Windows 11 that was causing boot failures with the error "UNMOUNTABLE_BOOT_VOLUME" on some professional systems after the installation of recent security updates. The fix was deployed via update KB5077181 as part of the February 2026 Patch Tuesday. The issue specifically affected commercial machines and was related to failures during the application of updates. No CVE or additional technical details were mentioned.