The remote host is missing an update to netkit-telnet-ssl announced via advisory DSA 616-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20616-1

Joel Eriksson discovered a format string vulnerability in telnetd-ssl which may be able to lead to the execution of arbitrary code on the victims machine. For the stable distribution (woody) this problem has been fixed in version 0.17.17+0.1-2woody3. For the unstable distribution (sid) this problem has been fixed in version 0.17.24+0.1-6. We recommend that you upgrade your immediately package.