The ValidateUserLogon function in provider/libserver/ECSession.cpp in Zarafa 5.00 before 7.1.8 beta2 allows remote attackers to cause a denial of service (crash) via vectors related to "a NULL pointer of the username."
https://bugzilla.redhat.com/show_bug.cgi?id=1059903
https://bugzilla.redhat.com/show_bug.cgi?id=1056767
http://www.openwall.com/lists/oss-security/2014/01/31/14
http://www.mandriva.com/security/advisories?name=MDVSA-2014:044