The Logging Server (ftplogsrv.exe) 7.9.14.0 and earlier in IPSwitch WS_FTP 6.1 allows remote attackers to cause a denial of service (loss of responsiveness) via a large number of large packets to port 5151/udp, which causes the listening socket to terminate and prevents log commands from being recorded, a different vulnerability than CVE-2007-3823.
http://www.vupen.com/english/advisories/2008/0408
http://www.securityfocus.com/bid/27612
http://www.securityfocus.com/archive/1/487506/100/0/threaded