FTP servers such as OpenBSD ftpd, NetBSD ftpd, ProFTPd and Opieftpd do not properly cleanse untrusted format strings that are used in the setproctitle function (sometimes called by set_proc_title), which allows remote attackers to cause a denial of service or execute arbitrary commands.
http://www.securityfocus.com/bid/1438
http://www.securityfocus.com/bid/1425
http://www.cert.org/advisories/CA-2000-13.html
http://archives.neohapsis.com/archives/bugtraq/2000-07/0121.html
http://archives.neohapsis.com/archives/bugtraq/2000-07/0061.html
http://archives.neohapsis.com/archives/bugtraq/2000-07/0031.html