Published: 3 May 2012
sapi/cgi/cgi_main.c in PHP before 5.3.12 and 5.4.x before 5.4.2, when configured as a CGI script (aka php-cgi), does not properly handle query strings that lack an = (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.
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.
Fix was incomplete, see CVE-2012-2311