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.
https://access.redhat.com/errata/RHSA-2019:2782
https://access.redhat.com/errata/RHSA-2019:2781
https://access.redhat.com/errata/RHSA-2019:2780
https://access.redhat.com/errata/RHSA-2019:2779
https://access.redhat.com/errata/RHSA-2019:2778
https://access.redhat.com/errata/RHSA-2019:2777
https://access.redhat.com/errata/RHSA-2019:1400
https://access.redhat.com/errata/RHSA-2019:1399
https://access.redhat.com/errata/RHSA-2019:1398
https://access.redhat.com/errata/RHSA-2019:0886