The kpasswd service provided by kadmind was vulnerable to a UDP
"ping-pong" attack [CVE-2002-2443].  Don't respond to packets unless
they pass some basic validation, and don't respond to our own error
packets.

Some authors use CVE-1999-0103 to refer to the kpasswd UDP ping-pong
attack or UDP ping-pong attacks in general, but there is discussion
leading toward narrowing the definition of CVE-1999-0103 to the echo,
chargen, or other similar built-in inetd services.

https://github.com/krb5/krb5/commit/cf1a0c411b2668c57c41e9c4efd15ba17b6b322ccvs
Fix CVE-2002-2443 in mit-krb5