While investigating bug PROTON-2014, we discovered that under some circumstances Apache Qpid Proton versions 0.9 to 0.27.0 (C library and its language bindings) can connect to a peer anonymously using TLS *even when configured to verify the peer certificate* while used with OpenSSL versions before 1.1.0. This means that an undetected man in the middle attack could be constructed if an attacker can arrange to intercept TLS traffic.
CVE Vulnerability