The remote host is missing an update to libpng2, libpng3 announced via advisory DSA 140-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20140-1

Developers of the PNG library have fixed a buffer overflow in the progressive reader when the PNG datastream contains more IDAT data than indicated by the IHDR chunk. Such deliberately malformed datastreams would crash applications which could potentially allow an attacker to execute malicious code. Programs such as Galeon, Konquerer and various others make use of these libraries. To find out which packages depend on this library, you may want to execute the following commands: apt-cache showpkg libpng2 apt-cache showpkg libpng3 This problem has been fixed in version 1.0.12-3.woody.1 of libpng and version 1.2.1-1.1.woody.1 of libpng3 for the current stable distribution (woody) and in version 1.0.12-4 of libpng and version 1.2.1-2 of libpng3 for the unstable distribution (sid). We recommend that you upgrade your libpng packages immediately and