http://web.mit.edu/kerberos/advisories/2011-006-patch-r18.txt

diff -Naurp krb5-1.8.1/src/plugins/kdb/db2/lockout.c krb5-1.8.1.oden/src/plugins/kdb/db2/lockout.c
--- krb5-1.8.1/src/plugins/kdb/db2/lockout.c	2009-11-24 23:52:25.000000000 +0000
+++ krb5-1.8.1.oden/src/plugins/kdb/db2/lockout.c	2011-10-22 08:14:06.000000000 +0000
@@ -158,13 +158,23 @@ krb5_db2_lockout_audit(krb5_context cont
         return 0;
     }
 
+    if (entry == NULL)
+        return 0;
+
     code = lookup_lockout_policy(context, entry, &max_fail,
                                  &failcnt_interval,
                                  &lockout_duration);
     if (code != 0)
         return code;
 
-    assert (!locked_check_p(context, stamp, max_fail, lockout_duration, entry));
+    /*
+     * Don't continue to modify the DB for an already locked account.
+     * (In most cases, status will be KRB5KDC_ERR_CLIENT_REVOKED, and
+     * this check is unneeded, but in rare cases, we can fail with an
+     * integrity error or preauth failure before a policy check.)
+     */
+    if (locked_check_p(context, stamp, max_fail, lockout_duration, entry))
+        return 0;
 
     if (status == 0 && (entry->attributes & KRB5_KDB_REQUIRES_PRE_AUTH)) {
         /*
diff -Naurp krb5-1.8.1/src/plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c krb5-1.8.1.oden/src/plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c
--- krb5-1.8.1/src/plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c	2011-10-22 08:13:47.000000000 +0000
+++ krb5-1.8.1.oden/src/plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c	2011-10-22 08:14:06.000000000 +0000
@@ -131,6 +131,7 @@ krb5_ldap_get_principal(krb5_context con
     CHECK_LDAP_HANDLE(ldap_context);
 
     if (is_principal_in_realm(ldap_context, searchfor) != 0) {
+        st = KRB5_KDB_NOENTRY;
         *more = 0;
         krb5_set_error_message (context, st, "Principal does not belong to realm");
         goto cleanup;
diff -Naurp krb5-1.8.1/src/plugins/kdb/ldap/libkdb_ldap/lockout.c krb5-1.8.1.oden/src/plugins/kdb/ldap/libkdb_ldap/lockout.c
--- krb5-1.8.1/src/plugins/kdb/ldap/libkdb_ldap/lockout.c	2009-11-24 23:52:25.000000000 +0000
+++ krb5-1.8.1.oden/src/plugins/kdb/ldap/libkdb_ldap/lockout.c	2011-10-22 08:14:06.000000000 +0000
@@ -150,15 +150,25 @@ krb5_ldap_lockout_audit(krb5_context con
         return 0;
     }
 
+    if (entry == NULL)
+        return 0;
+
     code = lookup_lockout_policy(context, entry, &max_fail,
                                  &failcnt_interval,
                                  &lockout_duration);
     if (code != 0)
         return code;
 
-    entry->mask = 0;
+    /*
+     * Don't continue to modify the DB for an already locked account.
+     * (In most cases, status will be KRB5KDC_ERR_CLIENT_REVOKED, and
+     * this check is unneeded, but in rare cases, we can fail with an
+     * integrity error or preauth failure before a policy check.)
+     */
+    if (locked_check_p(context, stamp, max_fail, lockout_duration, entry))
+        return 0;
 
-    assert (!locked_check_p(context, stamp, max_fail, lockout_duration, entry));
+    entry->mask = 0;
 
     if (status == 0 && (entry->attributes & KRB5_KDB_REQUIRES_PRE_AUTH)) {
         /*