Double free vulnerability in the authentication and authentication token alteration code in PAM-MySQL 0.6.x before 0.6.2 and 0.7.x before 0.7pre3 allows remote attackers to cause a denial of service (application crash) and possibly execute arbitrary code via crafted passwords, which lead to a double free of a pointer that was created by the pam_get_item function.  NOTE: this issue only occurs in certain configurations in which there are multiple PAM modules, PAM-MySQL is not evaluated first, and there are no requisite modules before PAM-MySQL.