sshd in OpenSSH 3.2.2, when using YP with netgroups and under certain conditions, may allow users to successfully authenticate and log in with another user's password.
http://www.securityfocus.com/bid/4803
http://www.openbsd.org/errata.html#sshbsdauth
http://www.iss.net/security_center/static/9215.php
http://archives.neohapsis.com/archives/bugtraq/2002-05/0235.html