mnet/xmlrpc/client.php in MNET in Moodle 1.9.x before 1.9.14, 2.0.x before 2.0.5, and 2.1.x before 2.1.2 does not properly process the return value of the openssl_verify function, which allows remote attackers to bypass validation via a crafted certificate.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.