The remote host is missing an update to netpbm-free announced via advisory DSA 263-1.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%20263-1

Al Viro and Alan Cox discovered several maths overflow errors in NetPBM, a set of graphics conversion tools. These programs are not installed setuid root but are often installed to prepare data for processing. These vulnerabilities may allow remote attackers to cause a denial of service or execute arbitrary code. For the stable distribution (woody) this problem has been fixed in version 9.20-8.2. The old stable distribution (potato) does not seem to be affected by this problem. For the unstable distribution (sid) this problem has been fixed in version 9.20-9. We recommend that you upgrade your netpbm package.