Buffer overflow in Ipswitch WS_FTP Server with SSH 6.1.0.0 allows remote authenticated users to cause a denial of service (crash) and possibly execute arbitrary code via a long opendir command.
https://www.exploit-db.com/exploits/5044
http://www.vupen.com/english/advisories/2008/0400/references
http://www.securityfocus.com/bid/27573
http://www.securityfocus.com/archive/1/487441/100/0/threaded