UNMOUNTABLE_BOOT_VOLUME
Windows 11 KB5077181 fixes boot failures linked to failed updates
Microsoft says it has resolved a Windows 11 bug that caused some commercial systems to fail to boot with an “UNMOUNTABLE_BOOT_VOLUME” error after installing recent security updates, with the fix delivered in the February 2026 Patch Tuesday update. The boot issue, which Microsoft previously investigated and linked to failed December 2025 updates, affected a limited number of […]
Microsoft links Windows 11 boot failures to failed December 2025 update
Microsoft has linked recent reports of Windows 11 boot failures after installing the January 2026 updates to previously failed attempts to install the December 2025 security update, which left systems in an “improper state.” The boot failures were first reported earlier this month after users installed the January 2026 Patch Tuesday cumulative update, KB5074109, on Windows 11 […]
Microsoft investigates Windows 11 boot failures after January updates
Microsoft is investigating reports that some Windows 11 devices are failing to boot with “UNMOUNTABLE_BOOT_VOLUME” errors after installing the January 2026 Patch Tuesday security updates. The issue affects Windows 11 version 25H2 and all editions of Windows 11 version 24H2 after installing the KB5074109 cumulative update released as part of this month’s updates. According to Microsoft, some customers have […]