Windows 11 January 2026 update chaos: Microsoft probes boot failures as emergency fixes pile up
Microsoft is investigating Windows 11 boot failures tied to January security updates, with some users seeing “UNMOUNTABLE_BOOT_VOLUME” errors. Affected devices may need manual recovery, though virtual machines appear unaffected. On Jan. 24, Microsoft released patch KB5078127 to fix cloud storage and Outlook hangs. The company has not identified the root cause of the boot issues.
