What is WU-0x800b0100?
WU-0x800b0100 shows up as a high-severity Windows operating system fault. No signature was present in the subject. This error indicates that the downloaded update files are missing digital signatures or have been corrupted, causing trust verification to fail. See the troubleshooting steps below for the fix.
Common Causes
- Interrupted downloads causing incomplete or corrupt file packages inside the update cache.
- Corruption inside the Cryptographic Services database files responsible for verifying file signatures.
- Third-party security software intercepting and modifying update files during download.
Step-by-Step Fix Guide
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1
Run DISM RestoreHealth and System File Checker (SFC) to repair corrupted components.
"Run DISM RestoreHealth and System File Checker (SFC) to repair corrupted components." is worth trying when interrupted downloads causing incomplete or corrupt file packages inside the update cache turns out to be the culprit.
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2
Restart and rebuild the Cryptographic Services catalog directories.
"Restart and rebuild the Cryptographic Services catalog directories." targets corruption inside the Cryptographic Services database files responsible for verifying file signatures, one of the documented causes of WU-0x800b0100.
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3
Purge the SoftwareDistribution download directory and re-initiate the update.
"Purge the SoftwareDistribution download directory and re-initiate the update." targets interrupted downloads causing incomplete or corrupt file packages inside the update cache, one of the documented causes of WU-0x800b0100.
Commands & Diagnostics
DISM /Online /Cleanup-Image /RestoreHealth
net stop cryptsvc
net start cryptsvc
Frequently Asked Questions
In most cases, interrupted downloads causing incomplete or corrupt file packages inside the update cache is behind WU-0x800b0100. Corruption inside the Cryptographic Services database files responsible for verifying file signatures and third-party security software intercepting and modifying update files during download can trigger it too.
"Run DISM RestoreHealth and System File Checker (SFC) to repair corrupted components" clears up most WU-0x800b0100 reports by itself. The remaining steps above cover what's left.
Rated high severity — WU-0x800b0100 isn't immediately destructive, but recurring instances are a sign to fix it sooner rather than later.
In most cases, yes — the guide above resolves WU-0x800b0100 without a clean install. Treat a reinstall as the last resort, not the first move.
Sometimes. Microsoft regularly releases patches that fix known BSOD triggers including WU-0x800b0100. Make sure Windows is fully up to date via Settings → Windows Update before attempting more advanced fixes.
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