Windows 11 appears to have a boot failure bug that's caused by an update failure bug, creating a circle of, err, bugs

Round and round we go.
Bleeping Computer

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 ...
XDA Developers on MSN

Microsoft confirms that a stack of bad Windows updates is causing boot issues

It's not just January's one.

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 ...