freeFTPd.exe in freeFTPd through 1.0.11 allows remote attackers to bypass authentication via a crafted SFTP session, as demonstrated by an OpenSSH client with modified versions of ssh.c and sshconnect2.c.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2012-5941
http://archives.neohapsis.com/archives/fulldisclosure/2012-12/0011.html