CVE-2019-0223

A cryptographic weakness was discovered in qpid-proton’s use of TLS. If the qpid-proton client was used without client certificates, it would accept an anonymous cipher offered by the server. A man-in-the-middle attacker could use this to silently intercept traffic that should have been encrypted.

Mitigation

This attack will not work if client-certificate authentication is in place because anonymous ciphers would not then be available.
Another possible mitigation is to disable anonymous ciphers on clients.