core/database_api.php in Mantis 0.19.0a1 through 1.0.0a3, with register_globals enabled, allows remote attackers to connect to internal databases by modifying the g_db_type variable and monitoring the speed of responses, as identified by bug#0005956.
http://www.securityfocus.com/bid/14604
http://www.gentoo.org/security/en/glsa/glsa-200509-16.xml
http://www.debian.org/security/2005/dsa-778