bip before 0.8.6 allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via an empty USER command.
https://bugzilla.redhat.com/show_bug.cgi?id=630437
http://www.vupen.com/english/advisories/2011/0096
http://www.securityfocus.com/bid/42995
http://www.openwall.com/lists/oss-security/2010/09/07/6
http://www.openwall.com/lists/oss-security/2010/09/05/1
http://secunia.com/advisories/42889
http://lists.fedoraproject.org/pipermail/package-announce/2011-January/052992.html