Squid 3.0 through 3.0.STABLE16 and 3.1 through 3.1.0.11 does not properly enforce "buffer limits and related bound checks," which allows remote attackers to cause a denial of service via (1) an incomplete request or (2) a request with a large header size, related to (a) HttpMsg.cc and (b) client_side.cc.
http://www.vupen.com/english/advisories/2009/2013
http://www.squid-cache.org/Versions/v3/3.1/changesets/b9654.patch
http://www.squid-cache.org/Advisories/SQUID-2009_2.txt
http://www.securitytracker.com/id?1022607
http://www.securityfocus.com/bid/35812
http://www.mandriva.com/security/advisories?name=MDVSA-2009:178
http://www.mandriva.com/security/advisories?name=MDVSA-2009:161