A squid security update has been released for Debian 6 LTS

Package : squid
Version : 2.7.STABLE9-2.1+deb6u1
CVE ID : CVE-2014-3609

CVE-2014-3609: Denial of Service in Range header processing.

Ignore Range headers with unidentifiable byte-range values. If squid is
unable to determine the byte value for ranges, treat the header as
invalid.