Microsoft investigates Windows 11 boot failure following January cumulative update. There reports that the January 2026 security update, released on January 13, has left certain Windows 11 devices unable to boot. Affected systems display a black screen with the message, "Your device ran into a problem and needs a restart. You can restart," accompanied by the stop code "UNMOUNTABLE_BOOT_VOLUME." At this stage, the device cannot complete startup and requires manual boot recovery.
The issue appears to impact devices running Windows 11 versions 24H2 and 25H2. Microsoft characterizes the reports as limited in number but has not disclosed the cause of the issue. There is no provided workaround as well. Users encountering this failure must enter the Windows Recovery Environment to uninstall the January 2026 security patch manually. The company continues to explore potential fixes and workarounds.
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Recovering the OS
Users encountering the unbootable state after installing update KB5074109 should access the Windows Recovery Environment by repeatedly interrupting the startup process during the Power-On Self-Test phase, which triggers automatic recovery mode. Once inside WinRE, navigate to Troubleshoot, select Advanced options, then choose Uninstall Updates and remove the latest quality update using administrator credentials. This manual removal process resolves the boot failure when normal desktop access remains unavailable.
This boot failure is the last in the set of issues coming from Microsoft's January Patch Tuesday releases. Earlier issues included systems running version 23H2 that could not shut down or hibernate, and devices on versions 24H2 and 25H2 that failed to sign in via Remote Desktop. Subsequently, cloud-backed applications such as Outlook, Dropbox, and OneDrive became inoperable for some users. All those bugs were fixed with out-of-the-band updates.
While Microsoft has already deployed two out-of-band updates to resolve the application and sign-in problems, the company has not yet released a fix for the boot failure issue. I think we can expect another emergency update to follow.
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