The remote host is missing an update to libpng announced via advisory DSA 2287-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%202287-1

The PNG library libpng has been affected by several vulnerabilities. The most critical one is the identified as CVE-2011-2690. Using this vulnerability, an attacker is able to overwrite memory with an arbitrary amount of data controlled by her via a crafted PNG image. The other vulnerabilities are less critical and allow an attacker to cause a crash in the program (denial of service) via a crafted PNG image. For the oldstable distribution (lenny), this problem has been fixed in version 1.2.27-2+lenny5. Due to a technical limitation in the Debian archive processing scripts, the updated packages cannot be released in paralell with the packages for Squeeze. They will appear shortly. For the stable distribution (squeeze), this problem has been fixed in version 1.2.44-1+squeeze1. For the unstable distribution (sid), this problem has been fixed in version 1.2.46-1. We recommend that you upgrade your libpng packages.