The remote host is missing an update to wu-ftpd announced via advisory DSA 705-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20705-1

Several denial of service conditions have been discovered in wu-ftpd, the popular FTP daemon. The Common Vulnerabilities and Exposures project identifies the following problems: CVE-2005-0256 Adam Zabrocki discovered a denial of service condition in wu-ftpd that could be exploited by a remote user and cause the server to slow down the server by resource exhaustion. CVE-2003-0854 Georgi Guninski discovered that /bin/ls may be called from within wu-ftpd in a way that will result in large memory consumption and hence slow down the server. For the stable distribution (woody) these problems have been fixed in version 2.6.2-3woody5. For the unstable distribution (sid) these problems have been fixed in version 2.6.2-19. We recommend that you upgrade your wu-ftpd package.