Thunderbird 140.1.0esr can't send messages (Palo Alto FW issue)

sollericos · 07-29-2025, 04:56 AM

Hi.

After upgrading TB to 140.1.0esr everything went ok at home, but not at work, where I couldn't send any message.

The issue is that TB has increased the security by PQC (I've read about this at Kyber + X25519) but our Palo Alto Firewall doesn't trust this new interchange key negotiation and discards those packets. Maybe it's happening to others FW.

The TEMPORARY solution proposed is setting "security.tls.enable_kyber" to "false" until your FW get updated to support PQC.

I hope this can help someone.

bitfuzzy · 08-08-2025, 10:23 AM

I don't use Palo Alto, but it looks like this can be adjusted in the config for the Palo Alto -
https://docs.paloaltonetworks.com/ne...m-cryptography

sollericos · 08-13-2025, 04:34 AM

Thanks, bitfuzzy. I've sent this link to the security team for review.