MyBB (aka MyBulletinBoard) before 1.4.12 does not properly restrict uid values for group join requests, which allows remote attackers to cause a denial of service (resource consumption) by using guest access to submit join request forms for moderated groups, related to usercp.php and managegroup.php.
https://exchange.xforce.ibmcloud.com/vulnerabilities/64513
http://openwall.com/lists/oss-security/2010/12/06/2
http://openwall.com/lists/oss-security/2010/10/11/8
http://openwall.com/lists/oss-security/2010/10/08/7
http://dev.mybboard.net/projects/mybb/repository/revisions/4856
http://dev.mybboard.net/issues/722
http://blog.mybb.com/2010/04/13/mybb-1-4-12-released-security-maintenance-update/