krb5 is vulnerabl eto denial of service. Multiple NULL pointer dereference and assertion failure flaws were found in the MIT Kerberos KDC when it was configured to use an LDAP (Lightweight Directory Access Protocol) or Berkeley Database (Berkeley DB) back end. A remote attacker could use these flaws to crash the KDC.
bugs.debian.org/cgi-bin/bugreport.cgi?bug=629558
web.mit.edu/kerberos/advisories/MITKRB5-SA-2011-006.txt
www.kb.cert.org/vuls/id/659251
www.mandriva.com/security/advisories?name=MDVSA-2011:159
www.redhat.com/support/errata/RHSA-2011-1379.html
access.redhat.com/errata/RHSA-2011:1379
access.redhat.com/security/updates/classification/#moderate