Published: 04 May 2012
sapi/cgi/cgi_main.c in PHP before 5.3.13 and 5.4.x before 5.4.3, when configured as a CGI script (aka php-cgi), does not properly handle query strings that contain a %3D sequence but no = (equals sign) character, which allows remote attackers to execute arbitrary code by placing command-line options in the query string, related to lack of skipping a certain php_getopt for the 'd' case. NOTE: this vulnerability exists because of an incomplete fix for CVE-2012-1823.
From the Ubuntu security team
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.
Please see http://www.php.net/archive/2012.php#id2012-05-06-1 for more details when using configurations other than as described in /usr/share/doc/php5-cgi/README.Debian.gz.