On certain error conditions, prep_reprocess_req() calls kdc_err() with
a null pointer as the format string, causing a null dereference and
denial of service.  Legitimate protocol requests can trigger this
problem.

https://github.com/krb5/krb5/commit/289555f989b42f2b8d13efe4904dc3515433d5e5
Commit By: tlyu
Revision: 23533
Changed Files:
U   trunk/src/kdc/do_tgs_req.c
U   trunk/src/lib/kadm5/logger.c