FtpXQ Server 3.0.1 allows remote attackers to cause a denial of service (CPU exhaustion) via a long MKD command.
https://exchange.xforce.ibmcloud.com/vulnerabilities/29778
http://www.vupen.com/english/advisories/2006/4192
http://securityreason.com/securityalert/1789
http://secunia.com/advisories/22540
http://lists.grok.org.uk/pipermail/full-disclosure/2006-October/050335.html