Error code
Firefox SEC_ERROR_UNKNOWN_ISSUER
FIREFOXSEC_ERROR_UNKNOWN_ISSUER
Browser Error Code· An error code shown in a web browser when a page fails to load.
What it means
Firefox does not recognize the authority that signed the certificate.
How to fix it
- Add a trusted exception only if you control the server and trust the certificate.
- If on a corporate network your IT department may need to add their CA to Firefox via AutoConfig or a managed policy.
- Never accept on public sites you do not control.
Not affiliated with Firefox. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.
More Firefox codes
- SEC_ERROR_BAD_DERThe certificate contains invalid DER-encoded data and cannot be parsed
- SEC_ERROR_CERT_SIGNATURE_ALGORITHM_DISABLEDThe certificate uses a signature algorithm that Firefox has disabled for security reasons
- SEC_ERROR_EXPIRED_CERTIFICATEThe server's certificate has expired and the connection cannot be secured
- SEC_ERROR_INADEQUATE_KEY_USAGEThe certificate is being used for a purpose not permitted by its key usage extension
- SEC_ERROR_OCSP_FUTURE_RESPONSEThe OCSP certificate status response is dated in the future
- SEC_ERROR_OCSP_INVALID_SIGNING_CERTThe certificate that signed the OCSP response is not trusted
- SEC_ERROR_REUSED_ISSUER_AND_SERIALA different certificate with the same issuer and serial number was already seen
- SEC_ERROR_REVOKED_CERTIFICATEThe certificate has been revoked by the authority that issued it
- MOZILLA_PKIX_ERROR_MITM_DETECTEDFirefox detected a likely man-in-the-middle attack on this connection
- MOZILLA_PKIX_ERROR_SELF_SIGNED_CERTThe certificate is self-signed and not issued by a trusted certificate authority
- SSL_ERROR_BAD_CERT_DOMAINThe certificate is valid but was issued for a different hostname
- SSL_ERROR_NO_CYPHER_OVERLAPFirefox and the server could not agree on any shared encryption algorithms