The remote host is missing an update to proftpd announced via advisory DSA 029-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20029-1

The following problems have been reported for the version of proftpd in Debian 2.2 (potato): 1. There is a memory leak in the SIZE command which can result in a denial of service, as reported by Wojciech Purczynski. This is only a problem if proftpd cannot write to its scoreboard file the default configuration of proftpd in Debian is not vulnerable. 2. A similar memory leak affects the USER command, also as reported by Wojciech Purczynski. The proftpd in Debian 2.2 is susceptible to this vulnerability an attacker can cause the proftpd daemon to crash by exhausting its available memory. 3. There were some format string vulnerabilities reported by Przemyslaw Frasunek. These are not known to have exploits, but have been corrected as a precaution. All three of the above vulnerabilities have been corrected in proftpd-1.2.0pre10-2potato1. We recommend you upgrade your proftpd package immediately.