libzmq (aka) ZeroMQ is vulnerable to bypassing security mechanisms or downgrade attacks. The vulnerability exists because ZMTP V3 protocol handler sends ZMTP v2 or earlier headers.
lists.fedoraproject.org/pipermail/package-announce/2015-May/159176.html
lists.opensuse.org/opensuse-updates/2015-06/msg00018.html
www.debian.org/security/2015/dsa-3255
bugzilla.redhat.com/show_bug.cgi?id=1221666
github.com/zeromq/libzmq/issues/1273
github.com/zeromq/zeromq4-x/commit/b6e3e0f601e2c1ec1f3aac880ed6a3fe63043e51