The mci_check_login function in api/soap/mc_api.php in the SOAP API in MantisBT before 1.2.9 allows remote attackers to bypass authentication via a null password.
https://github.com/mantisbt/mantisbt/commit/f5106be52cf6aa72c521f388e4abb5f0de1f1d7f
http://www.securityfocus.com/bid/52313
http://www.openwall.com/lists/oss-security/2012/03/06/9
http://www.mantisbt.org/bugs/view.php?id=13901
http://www.mantisbt.org/bugs/changelog_page.php?version_id=140
http://www.debian.org/security/2012/dsa-2500
http://security.gentoo.org/glsa/glsa-201211-01.xml
http://secunia.com/advisories/51199
http://secunia.com/advisories/49572
http://secunia.com/advisories/48258
http://lists.fedoraproject.org/pipermail/package-announce/2012-November/093064.html
http://lists.fedoraproject.org/pipermail/package-announce/2012-November/093063.html
http://lists.fedoraproject.org/pipermail/package-announce/2012-November/092926.html