Multiple Unix talkd/walld Escape Sequence Screen Disruption DoS
Remote / Network Access
Denial of Service,
Loss of Availability
Many Unix versions contain a flaw that may allow a remote attacker to interfere with a user's session. The issue is due to in.talkd and/or walld not sanitizing user-supplied input. By sending a crafted set of escape characters, it is possible to disrupt a user's session in a way that prevents their screen from displaying characters properly. This will force a user to reset the session (which frequently did not work) or exit the session and relogin.
Upgrade to one of the more recent versions of your flavor of Unix. Most (if not all) Unix vendors patched their various implementations many years ago.