MITRE description:

The parse_str function in PHP 4.x up to 4.4.0 and 5.x up to 5.0.5, when called with only one parameter, allows remote attackers to enable the register_globals directive via inputs that cause a request to be terminated due to the memory_limit setting, which causes PHP to set an internal flag that enables register_globals and allows attackers to exploit vulnerabilities in PHP applications that would otherwise be protected.