The remote host is missing an update to wu-ftpd announced via advisory DSA 377-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20377-1

wu-ftpd, an FTP server, implements a feature whereby multiple files can be fetched in the form of a dynamically constructed archive file, such as a tar archive. The names of the files to be included are passed as command line arguments to tar, without protection against them being interpreted as command-line options. GNU tar supports several command line options which can be abused, by means of this vulnerability, to execute arbitrary programs with the privileges of the wu-ftpd process. Georgi Guninski pointed out that this vulnerability exists in Debian woody. For the stable distribution (woody) this problem has been fixed in version 2.6.2-3woody2. For the unstable distribution (sid) this problem will be fixed soon. We recommend that you update your wu-ftpd package.