plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c in MIT Kerberos 5 (aka krb5) 1.12.x and 1.13.x before 1.13.1, when the KDC uses LDAP, allows remote authenticated users to cause a denial of service (NULL pointer dereference and daemon crash) by creating a database entry for a keyless principal, as demonstrated by a kadmin "add_principal -nokey" or "purgekeys -all" command.
https://github.com/krb5/krb5/commit/04038bf3633c4b909b5ded3072dc88c8c419bf16
http://www.ubuntu.com/usn/USN-2498-1
http://www.securitytracker.com/id/1031376
http://www.securityfocus.com/bid/71680
http://lists.opensuse.org/opensuse-updates/2015-03/msg00061.html