A vulnerability has been discovered and corrected in squid:

The idnsGrokReply function in Squid before 3.1.16 does not properly
free memory, which allows remote attackers to cause a denial of
service (daemon abort) via a DNS reply containing a CNAME record
that references another CNAME record that contains an empty A record
(CVE-2011-4096).

The updated packages have been patched to correct this issue.