The remote host is missing an update to mailreader announced via advisory DSA 534-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20534-1

A directory traversal vulnerability was discovered in mailreader whereby remote attackers could view arbitrary files with the privileges of the nph-mr.cgi process (by default, www-data) via relative paths and a null byte in the configLanguage parameter. For the current stable distribution (woody), this problem has been fixed in version 2.3.29-5woody1. For the unstable distribution (sid), this problem will be fixed soon. We recommend that you update your mailreader package.