The remote host is missing an update to proftpd-dfsg announced via advisory DSA 2346-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202346-1

Several vulnerabilities were discovered in ProFTPD, an FTP server: ProFTPD incorrectly uses data from an unencrypted input buffer after encryption has been enabled with STARTTLS, an issue similar to CVE-2011-0411. CVE-2011-4130 ProFTPD uses a response pool after freeing it under exceptional conditions, possibly leading to remote code execution. (The version in lenny is not affected by this problem.) For the oldstable distribution (lenny), this problem has been fixed in version 1.3.1-17lenny8. For the stable distribution (squeeze), this problem has been fixed in version 1.3.3a-6squeeze4. For the testing distribution (wheezy) and the unstable distribution (sid), this problem has been fixed in version 1.3.4~rc3-2. We recommend that you upgrade your proftpd-dfsg packages.