FTPshell Server 3.38 allows remote authenticated users to cause a denial of service (application crash) by multiple connections and disconnections without using the QUIT command.
https://exchange.xforce.ibmcloud.com/vulnerabilities/21531
https://euvd.enisa.europa.eu/vulnerability/EUVD-2005-2427
http://www.securityfocus.com/bid/14382
http://securitytracker.com/id?1014580