Firefox SEC_ERROR_REUSED_ISSUER_AND_SERIAL — Certificate Error

Overview

Firefox SEC_ERROR_REUSED_ISSUER_AND_SERIAL error means a certificate with the same issuer and serial number already exists in the certificate store.

Key Details

• Certificate serial numbers must be unique per issuer
• Common in development environments using self-signed certificates
• Firefox caches certificates more aggressively than Chrome
• Regenerating a self-signed cert with the same serial triggers this
• Clearing the cert database resolves the conflict

Common Causes

• Self-signed certificate regenerated with the same serial number
• Development server certificate replaced without changing the serial
• Corporate proxy certificate reissued with duplicate serial
• Firefox certificate store has stale cached certificates
• Multiple services using certificates from the same private CA with serial collision

Steps

1. 1Delete the Firefox cert database: close Firefox, delete cert9.db from your Firefox profile folder
2. 2Profile location: about:support > Profile Folder > Open Folder
3. 3Alternatively: Preferences > Privacy & Security > View Certificates > delete the conflicting cert from Authorities tab
4. 4When regenerating self-signed certs, always increment the serial: openssl x509 -set_serial 0x$(openssl rand -hex 8)
5. 5Restart Firefox after certificate changes

Tags

More in Firefox Errors

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