mt-phpincgi.php in Hajime Fujimoto mt-phpincgi before 2015-05-15 does not properly restrict URLs, which allows remote attackers to conduct PHP object injection attacks and execute arbitrary PHP code via a crafted request, as exploited in the wild in May 2015.
Improper Control of Generation of Code The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.