A security update is stopping Windows 11 from starting. The January 2026 update KB5074109 is causing boot failures on Windows 11 versions 24H2 and 25H2. This results in a black screen or a restart loop with a specific error.

Your device ran into a problem and needs a restart. You can restart.

The error is a Blue Screen of Death (BSOD) with the stop code UNMOUNTABLEBOOTVOLUME (0xED). Microsoft is investigating, and there is no official fix yet. This post provides a verified workaround to get back into your system.

Why This Error Happens

The KB5074109 update changes core system files that manage how Windows talks to your storage drive. For some hardware, these changes cause a problem during boot. The operating system can't correctly access the primary boot partition, which triggers the 0xED error. This failure happens only on physical devices, not in virtual machines, suggesting a driver or storage controller conflict from the update.

How to Fix the KB5074109 Boot Failure (Workaround)

Since there's no official patch, the solution is to uninstall update KB5074109. The method depends on whether you can get into Windows or are stuck in a boot loop.

Method 1: Uninstall from Within Windows (If System Boots)

If your computer can still load Windows, follow these steps to remove the update and stop it from coming back.

  1. Open Settings (Windows Key + I).
  2. Go to Windows Update > Update history.
  3. Click on Uninstall updates.
  4. Find Security Update for Microsoft Windows (KB5074109) in the list. Select it and click Uninstall.
  5. After your PC restarts, go back to Settings > Windows Update and select Pause updates for the maximum time (usually 7 weeks). This stops Windows from automatically reinstalling KB5074109.

Method 2: Uninstall from Windows Recovery Environment (WinRE) - For Boot Loops

If your system won't start and is stuck in a boot loop or black screen, use the Windows Recovery Environment.

You will need: A working Windows 11 PC to create a bootable USB flash drive using the Media Creation Tool.

  1. Create the Windows 11 installation media on another computer.
  2. Insert the USB flash drive into the computer that won't boot.
  3. Boot from the USB drive. You might need to press a key (like F12, F2, ESC, or DEL) during startup to get to the boot menu or UEFI/BIOS settings.
  4. On the Windows Setup screen, pick your language and click Next.
  5. Don't click "Install now." Instead, click Repair your computer in the lower-left corner.
  6. Choose Troubleshoot > Advanced options > Uninstall Updates.
  7. Select Uninstall latest quality update. This removes KB5074109.
  8. The process will finish and your PC will restart. Take out the USB drive and let the system boot normally from its internal drive.

Note: If you can't get into WinRE this way, you might need to do a clean installation of Windows 11 using the same USB media. This will erase everything on the system drive. Back up your data first if you can.

What to Do Next

This is a temporary fix. Microsoft is working on a corrected update. After you uninstall KB5074109, watch for official news about a fixed security update. Don't try to reinstall KB5074109 until Microsoft says the problem is fixed.

For other common Windows errors, see our guides on fix printer error 0x0000011b or fix Outlook error 0xc0000409.

This post will be updated when an official fix is released.

Need hands-on help? Contact our team.

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