The lookup_lockout_policy function in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) 1.8 through 1.8.4 and 1.9 through 1.9.1, when the db2 (aka Berkeley DB) or LDAP back end is used, allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via vectors that trigger certain process_as_req errors.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.