Windows & BSOD · medium

How to fix0x800B0109

0x800B0109 - Untrusted Root Certificate Error

What this error means

0x800B0109 - Untrusted Root Certificate Error (0x800B0109) is a medium-severity fault affecting the Windows operating system. A certificate chain processed, but terminated in a root certificate which is not trusted by the trust provider. Commonly occurs during Windows Update downloads, driver installation, or app installation when registry certificates are missing. Common triggers are corrupt cryptographic store components and network proxy SSL redirection interferences. See the troubleshooting steps below for the fix.

Before you begin

Save open work and back up important files. Note any recent driver or hardware changes. If Windows cannot start, use the startup guide first.

Work through these checks

0 of 4 complete
01Manually update root certificates in Windows

Manually update root certificates in Windows.

Use the instructions for your exact device and operating system. Check the manufacturer’s documentation before changing firmware, hardware, or system settings.

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02Reset cryptographic services folder via Command Prompt

Reset cryptographic services folder via Command Prompt.

Use the instructions for your exact device and operating system. Check the manufacturer’s documentation before changing firmware, hardware, or system settings.

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03Run SFC tool to verify system driver directories

Run SFC tool to verify system driver directories.

Use the instructions for your exact device and operating system. Check the manufacturer’s documentation before changing firmware, hardware, or system settings.

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04Configure network credentials to bypass proxy blocks

Configure network credentials to bypass proxy blocks.

Use the instructions for your exact device and operating system. Check the manufacturer’s documentation before changing firmware, hardware, or system settings.

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Possible causes

  • Outdated Windows root certificate database
  • Corrupt cryptographic store components
  • Malicious or self-signed driver certificate override
  • Network proxy SSL redirection interferences