The htcpHandleTstRequest function in htcp.c in Squid 2.x before 2.6.STABLE24 and 2.7 before 2.7.STABLE8, and htcp.cc in 3.0 before 3.0.STABLE24, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via crafted packets to the HTCP port.
http://www.vupen.com/english/advisories/2010/0603
http://www.vupen.com/english/advisories/2010/0371
http://www.squid-cache.org/Versions/v3/3.0/changesets/3.0-ADV-2010_2.patch
http://www.squid-cache.org/Versions/v2/2.7/changesets/12600.patch
http://www.squid-cache.org/Advisories/SQUID-2010_2.txt
http://www.securitytracker.com/id?1023587
http://www.securityfocus.com/bid/38212
http://secunia.com/advisories/38812
http://lists.fedoraproject.org/pipermail/package-announce/2010-March/037159.html
http://lists.fedoraproject.org/pipermail/package-announce/2010-February/035961.html