WS_FTP 5.0.2 allows remote authenticated users to cause a denial of service (CPU consumption) via a CD command that contains an invalid path with a "../" sequence.
https://exchange.xforce.ibmcloud.com/vulnerabilities/17155
https://euvd.enisa.europa.eu/vulnerability/EUVD-2004-1637
http://www.securityfocus.com/bid/11065