0x800B0109SystemHigh

Error 0x800B0109 — Untrusted Root (CERT_E_UNTRUSTEDROOT) | Windows System Error Fix

Windows 11Windows 10Windows Server 2022Windows 8.1

What Does 0x800B0109 Mean?

A certificate chain processed but terminated in a root certificate which is not trusted by the trust provider.

Real-World Causes

1Root certificate authority not in the Trusted Root Certification Authorities store
2Corporate proxy using its own root certificate not trusted by the client
3Outdated root certificate store
4Malware installed a fake root certificate

Symptoms

⚠Windows Update fails with untrusted root error
⚠HTTPS websites show security warnings
⚠Software installation fails signature verification
⚠Code signing validation fails

DIY Fix

Beginner-friendly steps you can try at home

1Run Windows Update to update root certificates
2Check system date and time are correct
3Run 'sfc /scannow' to repair certificate stores
4Remove suspicious certificates from Trusted Root store in certmgr.msc

Advanced Fix

For experienced users and IT professionals

1Update roots manually: 'certutil -generateSSTFromWU roots.sst'
2In enterprise: ensure the corporate root CA certificate is deployed via Group Policy
3Check for rogue certificates: review certmgr.msc > Trusted Root Certification Authorities for unknown entries

Frequently Asked Questions

What is a root certificate?

Root certificates are the foundation of trust in digital security. They are issued by Certificate Authorities (CAs) like DigiCert, Let's Encrypt, etc. Windows maintains a list of trusted root CAs. If a certificate chain leads to an untrusted root, the entire chain is rejected.

Related Error Codes

0x800B0101Certificate Expired (CERT_E_EXPIRED)0x800B010AChaining Error (CERT_E_CHAINING)

About the Author

Windows Troubleshooting Team

Verified against official Microsoft documentation and real-world diagnostic data. Error behavior confirmed across Windows 10, Windows 11, and Windows Server.