Microsoft Investigates Windows 11 Boot Issues After January 2026 Updates
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Quick Summary
Microsoft is looking into reports of Windows 11 devices failing to boot with ‘UNMOUNTABLE_BOOT_VOLUME’ errors following the January 2026 Patch Tuesday updates. This issue affects Windows 11 version 25H2 and all editions of version 24H2 after the installation of cumulative update KB5074109. Users have reported that their systems display a stop error during boot, requiring manual recovery efforts to restart.
The Securityish Brief
Microsoft is currently investigating a significant issue affecting Windows 11 devices that are failing to boot after the January 2026 Patch Tuesday security updates. Specifically, users are encountering ‘UNMOUNTABLE_BOOT_VOLUME’ errors after installing cumulative update KB5074109, which was released on January 13, 2026. Reports indicate that affected systems are unable to start and display a black crash screen with a message stating, ‘Your device ran into a problem and needs a restart.’
This problem appears to impact only physical devices, with no reports of virtual machines being affected. Users have been advised to submit feedback through the Feedback Hub app as Microsoft looks into whether this behavior is linked to the recent updates.
In addition to this boot issue, Microsoft also released emergency out-of-band updates to address a separate problem that caused Outlook to freeze when PST files were stored in cloud services like OneDrive or Dropbox. This issue primarily affects enterprise environments where Outlook is commonly used.
Understanding the Risks of Update-Related Issues
The ‘UNMOUNTABLE_BOOT_VOLUME’ error can lead to significant downtime for users and organizations, requiring manual recovery efforts that may not be straightforward. This situation underscores the importance of having a reliable backup and recovery plan in place for critical systems.
As Microsoft continues its investigation, users should monitor their systems for any abnormal behavior following updates. Regularly checking for updates and understanding the implications of each can help mitigate risks associated with system failures.
Organizations should also ensure that they have proper support channels in place for users experiencing these issues, as timely assistance can help reduce the impact on productivity.
- Windows 11 version 25H2 is affected by the boot failure issue.
- All editions of Windows 11 version 24H2 are also impacted after installing KB5074109.
- The problem requires manual recovery efforts to restore functionality.
- Microsoft has released emergency updates to address other issues affecting Outlook.
- Users are encouraged to provide feedback through the Feedback Hub app.
Key Takeaways
- Check if your Windows 11 device is running version 25H2 or 24H2 and has the latest updates installed.
- If you encounter the ‘UNMOUNTABLE_BOOT_VOLUME’ error, prepare for manual recovery efforts.
- Regularly back up important data to avoid loss during system failures.
- Monitor your device for unusual behavior after updates and report issues to Microsoft.
- Utilize the Feedback Hub app to submit any feedback regarding boot issues.
Key Terms & Concepts
- UNMOUNTABLE_BOOT_VOLUME: In this article, ‘UNMOUNTABLE_BOOT_VOLUME’ refers to a stop error that prevents Windows 11 devices from booting properly.
- Patch Tuesday: Patch Tuesday is a term used to describe the day Microsoft releases security updates for its software products.
- cumulative update: A cumulative update is a collection of updates and fixes that are packaged together and released by Microsoft.
Read the original article here: https://www.bleepingcomputer.com/news/microsoft/microsoft-investigates-windows-11-boot-failures-after-january-updates/
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