The remote host is missing an update to libmcrypt announced via advisory DSA 228-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20228-1

Ilia Alshanetsky discovered several buffer overflows in libmcrypt, a decryption and encryption library, that originates in from improper or lacking input validation. By passing input which is longer then expected to a number of functions (multiple functions are affected) the user can successful make libmcrypt crash and may be able to insert arbitrary, malicious, code which will be executed under the user libmcrypt runs as, e.g. inside a web server. Another vulnerability exists in the way libmcrypt loads algorithms via libtool. When different algorithms are loaded dynamically, each time an algorithm is loaded a small part of memory is leaked. In a persistant enviroment (web server) this could lead to a memory exhaustion attack that will exhaust all avaliable memory by launching repeated requests at an application utilizing the mcrypt library. For the current stable distribution (woody) this problem has been fixed in version 2.5.0-1woody1. The old stable distribution (potato) does not contain libmcrypt packages. For the unstable distribution (sid) these problems have been fixed in version 2.5.5-1. We recommend that you upgrade your libmcrypt packages.