The remote host is missing an update to libcairo announced via advisory DSA 1542-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201542-1

Peter Valchev (Google Security) discovered a series of integer overflow weaknesses in Cairo, a vector graphics rendering library used by many other applications. If an application uses cairo to render a maliciously-crafted PNG image, the vulnerability allows the execution of arbitrary code. For the stable distribution (etch), these problems have been fixed in version 1.2.4-4.1+etch1. For the unstable distribution (sid), these problems have been fixed in version 1.4.10-1.1. We recommend that you upgrade your libcairo packages.