Microsoft has resolved a Windows 11 bug that caused some commercial systems running 25H2 and 24H2 to fail to boot with an “UNMOUNTABLE_BOOT_VOLUME” error after recent security updates. The full fix was delivered in the February 10, 2026 Patch Tuesday update KB5077181, though devices made unbootable before the fix may still need manual remediation and enterprises should contact Microsoft Support for Business. #Windows11 #KB5077181
Keypoints
- Microsoft fixed a Windows 11 boot bug that caused some commercial devices to become unbootable.
- Affected systems displayed “UNMOUNTABLE_BOOT_VOLUME” and required manual recovery to restore functionality.
- The issue was traced to failed December 2025 updates leaving devices in an improper state after rollback.
- An initial mitigation shipped in optional preview KB5074105 on January 29, 2026, with the complete fix in KB5077181 on February 10, 2026.
- Devices that were already unbootable may still need additional remediation and enterprises should contact Microsoft Support for Business.