The remote host is missing an update to a2ps announced via advisory DSA 612-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20612-1

Rudolf Polzer discovered a vulnerability in a2ps, a converter and pretty-printer for many formats to PostScript. The program did not escape shell meta characters properly which could lead to the execution of arbitrary commands as a privileged user if a2ps is installed as a printer filter. For the stable distribution (woody) this problem has been fixed in version 4.13b-16woody1 For the unstable distribution (sid) this problem has been fixed in version 4.13b-4.2. We recommend that you upgrade your a2ps package.