TYPSoft FTP Server 1.10 allows remote authenticated users to cause a denial of service (crash) by sending an APPE (append) command immediately followed by a DELE (delete) command without sending file data in between these two commands.
https://exchange.xforce.ibmcloud.com/vulnerabilities/54407
http://www.securitytracker.com/id?1023234
http://www.securityfocus.com/archive/1/508048/100/0/threaded