The remote host is missing an update to tinymux announced via advisory DSA 1317-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201317-1

duskwave discovered that tinymux, a text-based multi-user virtual world server, performs insufficient boundary checks when working with user-supplied data, which might lead to the execution of arbitary code. For the stable distribution (etch), this problem has been fixed in version 2.4.3.31-1etch1. We recommend that you upgrade your tinymux package.