This section specifies the format for the KRB_ERROR message. The fields included in the message are intended to return as much information as possible about an error. It is not expected that all the information required by the fields will be available for all types of errors. If the appropriate information is not available when the message is composed, the corresponding field will be left out of the message.
Note that since the KRB_ERROR message is not protected by any encryption, it is quite possible for an intruder to synthesize or modify such a message. In particular, this means that the client should not use any fields in this message for security-critical purposes, such as setting a system clock or generating a fresh authenticator. The message can be useful, however, for advising a user on the reason for some failure.