Bitvise WinSSHD before 2002-03-16 allows remote attackers to cause a denial of service (resource exhaustion) via a large number of incomplete connections that are not properly terminated, which are not properly freed by SSHd.
http://www.iss.net/security_center/static/8470.php
http://online.securityfocus.com/archive/1/262681
http://archives.neohapsis.com/archives/vulnwatch/2002-q1/0068.html