The FwdState::connectedToPeer method in FwdState.cc in Squid before 3.5.14 and 4.0.x before 4.0.6 does not properly handle SSL handshake errors when built with the --with-openssl option, which allows remote attackers to cause a denial of service (application crash) via a plaintext HTTP message.
http://www.squid-cache.org/Advisories/SQUID-2016_1.txt
http://www.securitytracker.com/id/1035045
http://lists.squid-cache.org/pipermail/squid-announce/2016-February/000038.html
http://lists.squid-cache.org/pipermail/squid-announce/2016-February/000037.html
http://lists.opensuse.org/opensuse-security-announce/2016-08/msg00040.html
http://lists.opensuse.org/opensuse-security-announce/2016-08/msg00010.html