Microsoft ties Windows 11 boot issues to December 2025 patch rollback
Microsoft says recent Windows 11 boot failures after the January 2026 updates are linked to devices that previously failed to install the December 2025 security update and were rolled back, leaving the system in an “improper state” that can prevent boot when applying new updates. The issue affects physical devices on Windows 11 versions 25H2 and 24H2; the BSOD stop error is UNMOUNTABLE_BOOT_VOLUME. A partial fix is being developed to stop new no-boot scenarios, but it won’t repair already-bootless machines or prevent the improper state from forming. The cause and scope are still under investigation, with no VM impact reported at this time.
