A cups security update has been released for Debian 6 LTS

Package : cups
Version : 1.4.4-7+squeeze8
CVE ID : CVE-2015-1158 CVE-2015-1159

Two critical vulnerabilities have been found in the CUPS printing
system:

CVE-2015-1158 - Improper Update of Reference Count
Cupsd uses reference-counted strings with global scope. When parsing
a print job request, cupsd over-decrements the reference count for a
string from the request. As a result, an attacker can prematurely
free an arbitrary string of global scope. They can use this to
dismantle ACLs protecting privileged operations, and upload a
replacement configuration file, and subsequently run arbitrary code
on a target machine.

This bug is exploitable in default configurations, and does not
require any special permissions other than the basic ability to
print.

CVE-2015-1159 - Cross-Site Scripting
A cross-site scripting bug in the CUPS templating engine allows the
above bug to be exploited when a user browses the web. This XSS is
reachable in the default configuration for Linux instances of CUPS,
and allows an attacker to bypass default configuration settings that
bind the CUPS scheduler to the localhost or loopback interface.