I am trying to reach an internal company website (www.gqma.drw), with a certificate chain rooted in a company certificate authority. This works fine in Chrome, and worked in Firefox on my previous computer. But i recently got a new machine, and something somewhere is not quite right. I get an error message looking like this (between the ~~~s): ~~~ Someone could be trying to impersonate the site and you should not continue. Web sites prove their identity via certificates. Firefox does not trust www.gqma.drw because its certificate issuer is unknown, the certificate is self-signed, or the server is not sending the correct intermediate certificates. Error code: SEC_ERROR_UNKNOWN_ISSUER View Certificate ~~~ If i click on the error code, i get these details: ~~~ https://www.gqma.drw/ Peer's Certificate issuer is not recognised. HTTP Strict Transport Security: false HTTP Public Key Pinning: false Certificate chain: -----BEGIN CERTIFICATE----- MIICczCCAhigAwIBAgIUcg0ZTKoxYO3E5288qtNnymZ/L6AwCgYIKoZIzj0EAwIw NzEMMAoGA1UEChMDRFJXMRQwEgYDVQQLDAtJU1NAZHJ3LmNvbTERMA8GA1UEAxMI U1NETlMgQ0EwHhcNMjIwMzA5MTQxOTAwWhcNMjQwMzA4MTQxOTAwWjA5MQwwCgYD VQQKEwNEUlcxFDASBgNVBAsMC0lTU0BkcncuY29tMRMwEQYDVQQDEwoqLmdxbWEu ZHJ3MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEfXDxyLTebEuPHmneR4faNHoQ PouLPrBqOKnDOW/T+eexbAHcghiZqcQHoHW/Qo/kNQZYPhoHeMZK1ACdvnFTUaOB /zCB/DAOBgNVHQ8BAf8EBAMCBaAwEwYDVR0lBAwwCgYIKwYBBQUHAwEwDAYDVR0T AQH/BAIwADAdBgNVHQ4EFgQUvuzqIs1O1ioHT3qF+olSZ3dDseEwHwYDVR0jBBgw FoAUjGD9eMez/VkLc5nlNkg/U6dBgmUwNQYIKwYBBQUHAQEEKTAnMCUGCCsGAQUF BzABhhlodHRwOi8vb2NzcC5pc3MuZHJ3L3NzZG5zMB8GA1UdEQQYMBaCCiouZ3Ft YS5kcneCCGdxbWEuZHJ3MC8GA1UdHwQoMCYwJKAioCCGHmh0dHA6Ly9jZXJ0cy5p c3MuZHJ3L3NzZG5zL2NybDAKBggqhkjOPQQDAgNJADBGAiEAtEj7K/C2IHMzh175 9TpPu74YktH/1WJM12zUNIioi30CIQDpLqn09bmTFDgQDkg+0YHu1YSBTlCArWYJ KUxQUa0KPQ== -----END CERTIFICATE----- -----BEGIN CERTIFICATE----- MIIB3DCCAYKgAwIBAgIUeLNrkgHyp2GhO6Ee4fyvVbGaUg0wCgYIKoZIzj0EAwIw OjEMMAoGA1UEChMDRFJXMRQwEgYDVQQLDAtJU1NAZHJ3LmNvbTEUMBIGA1UEAxML SVNTIFJvb3QgQ0EwHhcNMTcwMzAxMjA0MzAwWhcNMjcwMjI3MjA0MzAwWjA6MQww CgYDVQQKEwNEUlcxFDASBgNVBAsMC0lTU0BkcncuY29tMRQwEgYDVQQDEwtJU1Mg Um9vdCBDQTBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABAjg18NvaBfwKP0BC/9U Cppc1W2rfSqzsY4KCRIAubItoMyQ13zp25KjVg9IF7Uru7cWQcUMvwf4+2Gb/4m4 sFSjZjBkMA4GA1UdDwEB/wQEAwIBBjASBgNVHRMBAf8ECDAGAQH/AgEBMB0GA1Ud DgQWBBSA3cairIJP/ooZLqrq+L9hSNwxczAfBgNVHSMEGDAWgBSA3cairIJP/ooZ Lqrq+L9hSNwxczAKBggqhkjOPQQDAgNIADBFAiAgvGnmTJgMosKFYuRJ7HZMuD/p ZTNapVJltFiGzKAtewIhAJMVQ72U+m7kLNRw6ej7icBQ9d+T4MuhGyJEeYeX5wR4 -----END CERTIFICATE----- -----BEGIN CERTIFICATE----- MIICYjCCAgigAwIBAgIUDZxs4OPknZA8SgUkWZ7EncHkYVIwCgYIKoZIzj0EAwIw OjEMMAoGA1UEChMDRFJXMRQwEgYDVQQLDAtJU1NAZHJ3LmNvbTEUMBIGA1UEAxML SVNTIFJvb3QgQ0EwHhcNMTcwMzAxMjA0NDAwWhcNMjcwMjI3MjA0NDAwWjA3MQww CgYDVQQKEwNEUlcxFDASBgNVBAsMC0lTU0BkcncuY29tMREwDwYDVQQDEwhTU0RO UyBDQTBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABNsaSU2QU1Z5ktRf19DaXZk6 TrPko0TPZFTSYFH9bPxVJ4guUfGnN5nZ7vQajX2NJJLZEL9TZGYSsE8RD/ftcsij ge4wgeswDgYDVR0PAQH/BAQDAgGmMB0GA1UdJQQWMBQGCCsGAQUFBwMBBggrBgEF BQcDAjASBgNVHRMBAf8ECDAGAQH/AgEAMB0GA1UdDgQWBBSMYP14x7P9WQtzmeU2 SD9Tp0GCZTAfBgNVHSMEGDAWgBSA3cairIJP/ooZLqrq+L9hSNwxczA1BggrBgEF BQcBAQQpMCcwJQYIKwYBBQUHMAGGGWh0dHA6Ly9vY3NwLmlzcy5kcncvc3NkbnMw LwYDVR0fBCgwJjAkoCKgIIYeaHR0cDovL2NlcnRzLmlzcy5kcncvc3NkbnMvY3Js MAoGCCqGSM49BAMCA0gAMEUCIBU5FNCu7ZmE7H1Oautblig4iA5JIgOO+4D/do2c pQ8IAiEAkIdZb5Doptfk1C5uofcvww3E0ZrSG98ZJ2+TW9sz4VA= -----END CERTIFICATE----- ~~~ If i click 'View Certificate', i get a chain of three certificates: # Subject common name = *.gqma.drw, issuer common name = SSDNS CA, subject key ID = BE:EC:EA:22:CD:4E:D6:2A:07:4F:7A:85:FA:89:52:67:77:43:B1:E1 # Subject common name = SSDNS CA, issuer common name = ISS Root CA, subject key ID = 8C:60:FD:78:C7:B3:FD:59:0B:73:99:E5:36:48:3F:53:A7:41:82:65 # Subject common name = ISS Root CA, issuer common name = SS Root CA, subject key ID = 80:DD:C6:A2:AC:82:4F:FE:8A:19:2E:AA:EA:F8:BF:61:48:DC:31:73 If i go to Settings > Privacy & Security > View Certificates > Authorities, i can find both the SSDNS CA and ISS Root CA certificates. As far as i can tell, they are identical - i can open the certificate from 'View Certificate' and the corresponding one from the certificate manager and flip between tabs, and all the details are the same. I am using Firefox 120.0, via a flatpak, on Ubuntu 22. I have given the flatpak access to /etc/ssl/certs, where my company's internal CA certificates are located. To me, this seems like it should all work. The server has a certificate signed by an internal CA, which is signed by another internal CA, and both those internal CA certificates are in my certificate manager. So what is going wrong? Is there any way i can debug this?