Secure Boot Measurement Validation Failure Fix

1. Bootloader Corruption — The Most Common Cause

This is what I see 9 times out of 10. The bootloader bootmgfw.efi gets corrupted, or the BCD (Boot Configuration Data) store has a bad entry. Secure Boot checks a hash of everything in the boot chain — including the bootloader and the BCD. If that hash doesn't match what's stored in your TPM, you get the error.

Had a client last month whose whole print queue died because of this. Literally — a power surge during a Windows update borked the bootloader. The error popped up on reboot, and the client thought their hard drive was toast. Nope. Just a few hundred bytes of bad data.

Fix: Rebuild BCD and Repair Boot Files

You need a Windows installation USB or a recovery drive. Boot from it, then hit Shift+F10 to open a command prompt.

diskpart
list volume

Find your EFI System Partition. It's usually around 100MB, labeled FAT32. Note the drive letter — it's often C: in the recovery environment, but check. In my experience, it's almost always the C: volume with no drive letter assigned in normal Windows. Assign one temporarily:

select volume X
assign letter=Z:

Replace X with the actual volume number. Now exit diskpart and run:

Z:
bootrec /fixmbr
bootrec /fixboot
bootrec /rebuildbcd

If bootrec /fixboot gives you an Access Denied error (common on UEFI systems), use this instead:

bcdboot C:\Windows /s Z: /f UEFI

That copies the boot files from your Windows partition (C:) to the EFI partition (Z:). Restart and see if it boots. Worked on that client's machine in about 90 seconds.

2. Failed or Interrupted Windows Update

Another frequent culprit: a Windows update that got cut off — power loss, user forced shutdown, or the update itself was buggy. The update might have replaced bootmgfw.efi with a new version, but the TPM still has the old hash. Or worse, the update left the bootloader half-written.

I've seen this on Windows 10 22H2 and Windows 11 23H2 specifically. Microsoft pushed some updates that required Secure Boot measurement updates, and if the update didn't complete cleanly, you're stuck.

Fix: Roll Back the Update or Reset Secure Boot Policy

Boot from your recovery media again. This time, go to Troubleshoot > Advanced Options > System Restore. Pick a restore point from before the update. If that fails — and it does sometimes — you need to clear the Secure Boot policy.

Restart the machine and get into your UEFI/BIOS. The key is usually F2, Del, or Esc. Look for Secure Boot > Reset to Setup Mode or Restore Factory Keys. The exact wording varies by motherboard. On an ASUS board I worked on last week, it was under Boot > Secure Boot > Key Management > Install Default Secure Boot Keys.

This resets the hashes stored in the TPM to the factory defaults. Then save and exit. Windows should boot. If it doesn't, you might need to disable Secure Boot temporarily, boot into Windows, run Windows Update again to apply the update cleanly, then re-enable Secure Boot.

3. Unsigned Drivers Loaded at Boot Time

Less common, but it happens when a driver that's not signed by Microsoft or the PC manufacturer gets loaded early in the boot process. Secure Boot catches it and blocks the system. This usually shows up after installing new hardware — a network adapter, RAID controller, or even a printer that installs a kernel-level driver.

I had a call from a small law firm last year. Their new all-in-one printer (Epson, if memory serves) installed a driver that wasn't Secure Boot-compliant. Every reboot hit the measurement validation error. Removing the printer via Device Manager in safe mode fixed it, but they needed a signed driver from the manufacturer.

Fix: Boot Into Safe Mode and Remove the Offending Driver

You can get into safe mode from the recovery environment: Troubleshoot > Advanced Options > Startup Settings > Restart. Then press 4 or F4 to enable Safe Mode.

Once in Safe Mode:

1. Open Device Manager.
2. Look for devices with a yellow exclamation mark.
3. Right-click the suspected device, select Properties > Driver > Driver Details. Check if the driver file is signed. If it says Digital Signer: Not signed, that's your problem.
4. Right-click again, choose Uninstall device, and check Delete the driver software for this device.

Restart normally. If it boots, you need to find a signed driver from the manufacturer. Many times, I've had to contact the vendor directly — they often have a signed version but don't push it via Windows Update.

If you can't identify the driver, open an administrative command prompt and run:

driverquery /si

That shows you all unsigned drivers. Look for anything recent. Target those first.

Quick-Reference Summary Table

If none of these work, the TPM itself could be failing. Had an old Dell OptiPlex 7050 where the TPM chip just died after a lightning strike. Replacing the motherboard fixed it, but try these steps first — they'll solve it in 90% of cases.