client_side.cc in Squid before 3.5.18 and 4.x before 4.0.10 does not properly ignore the Host header when absolute-URI is provided, which allows remote attackers to conduct cache-poisoning attacks via an HTTP request.
http://bugs.squid-cache.org/show_bug.cgi?id=4501
http://lists.opensuse.org/opensuse-security-announce/2016-08/msg00010.html
http://lists.opensuse.org/opensuse-security-announce/2016-08/msg00040.html
http://lists.opensuse.org/opensuse-updates/2016-08/msg00069.html
https://access.redhat.com/errata/RHSA-2016:1139
https://access.redhat.com/errata/RHSA-2016:1140
https://security.gentoo.org/glsa/201607-01
http://www.debian.org/security/2016/dsa-3625
http://www.oracle.com/technetwork/topics/security/linuxbulletinapr2016-2952096.html
http://www.securitytracker.com/id/1035768
http://www.squid-cache.org/Advisories/SQUID-2016_7.txt
http://www.squid-cache.org/Versions/v3/3.5/changesets/squid-3.5-14039.patch