The remote host is missing an update to xtell announced via advisory DSA 121-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20121-1

Several security related problems have been found in the xtell package, a simple messaging client and server. In detail, these problems contain several buffer overflows, a problem in connection with symbolic links, unauthorized directory traversal when the path contains ... These problems could lead into an attacker being able to execute arbitrary code on the server machine. The server runs with nobody privileges by default, so this would be the account to be exploited. They have been corrected by backporting changes from a newer upstream version by the Debian maintainer for xtell. These problems are fixed in version 1.91.1 in the stable distribution of Debian and in version 2.7 for the testing and unstable distribution of Debian. We recommend that you upgrade your xtell packages immediately.