It was discovered that PHP, when used as a stand alone CGI processor for the Apache Web Server, did not properly parse and filter query strings. This could allow a remote attacker to execute arbitrary code running with the privilege of the web server. Configurations using mod_php5 and FastCGI were not vulnerable.
This update addresses the issue when the PHP CGI interpreter is configured using mod_cgi and mod_actions as described in /usr/share/doc/php5-cgi/README.Debian.gz; however, if an alternate configuration is used to enable PHP CGI processing, it should be reviewed to ensure that command line arguments cannot be passed to the PHP interpreter. Please see CVE-2012-2311 for more details and potential mitigation approaches.