Microsoft is currently investigating reports of boot failures affecting Windows 11 devices. The issues emerged following the installation of the January 2026 security updates.
Affected users have reported seeing the stop error “UNMOUNTABLE_BOOT_VOLUME” during startup. This error prevents the system from booting and displays a black screen with the message: “Your device ran into a problem and needs a restart. You can restart.”
The problem has impacted Windows 11 version 25H2 and all editions of version 24H2 after installing the cumulative KB5074109 update. Microsoft is reviewing whether the issue is linked directly to this update.
According to the company, only a limited number of devices have been affected so far. These are mainly physical devices, while virtual machines appear to be unaffected. Users experiencing the issue need to perform manual recovery steps to restart their systems.
Industry source AskWoody highlighted that Microsoft is encouraging affected users and administrators to report problems through the Feedback Hub app. The company confirmed: “We are investigating this issue and will confirm if it is a regression caused by a Windows update once we have more details.”
This boot error has caused concern among Windows 11 users worldwide. While Microsoft has not released a permanent fix yet, emergency updates addressing other issues—like Microsoft Outlook freezing when PST files are stored in cloud services—have already been deployed.
Experts advise users to avoid installing the update on critical devices until the investigation concludes. Users who have already installed the update should back up important data and prepare for potential recovery steps if their system fails to boot.
In other news read more about: Microsoft Advises Users to Uninstall Windows 11 January 2026 Update: Reasons Explained
Microsoft continues to monitor the situation and has promised a detailed update once the cause of the Windows 11 boot errors is confirmed. Users are urged to stay cautious and follow official guidance until a solution is released.
