Microsoft is looking into Windows 11 boot issues following the January updates.
- Jan 26
- 2 min read
Microsoft is looking into reports of some Windows 11 devices encountering "UNMOUNTABLE_BOOT_VOLUME" errors and failing to boot after the January 2026 Patch Tuesday security updates.
This problem impacts Windows 11 version 25H2 and all editions of Windows 11 version 24H2 following the installation of the KB5074109 cumulative update included in this month's updates.
Microsoft has noted that some customers have reported their systems not starting and showing a stop error during boot.
Microsoft is looking into Windows 11 boot issues following the January updates.
"Microsoft has acknowledged a limited number of reports regarding an issue where devices fail to boot, displaying the stop code 'UNMOUNTABLE_BOOT_VOLUME', after the installation of the January 2026 Windows security update (as specified in the Originating KBs above), released on January 13, 2026, and subsequent updates," Microsoft stated.
The company notes that affected devices will display a black Windows crash screen with the message, "Your device ran into a problem and needs a restart. You can restart."
Microsoft reports that the affected systems cannot boot into Windows and need manual recovery to restart.
Microsoft is looking into Windows 11 boot issues following the January updates.
Only physical devices are impacted by the bug, with no virtual machines affected so far.
As initially identified by AskWoody, Microsoft is requesting that affected users and administrators submit feedback through the Feedback Hub app and mentioned that they are investigating whether this issue is related to a Windows update.
"We are looking into this issue and will confirm if it is a regression caused by a Windows update once we have more details. We will update this documentation as soon as more information is verified," Microsoft stated.
Microsoft is looking into Windows 11 boot issues following the January updates.
Microsoft also released emergency out-of-band (OOB) updates on Saturday to resolve an issue that caused Microsoft Outlook to freeze when PST files are stored in cloud services like OneDrive or Dropbox.
The company noted that this issue mainly affects the Outlook class, which is commonly used in enterprise environments.
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