The kdb_ldap plugin in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) 1.9 through 1.9.1, when the LDAP back end is used, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a kinit operation with incorrect string case for the realm, related to the is_principal_in_realm, krb5_set_error_message, krb5_ldap_get_principal, and process_as_req functions.
http://www.redhat.com/support/errata/RHSA-2011-1379.html
http://www.mandriva.com/security/advisories?name=MDVSA-2011:159
http://www.kb.cert.org/vuls/id/659251
http://web.mit.edu/kerberos/advisories/MITKRB5-SA-2011-006.txt