The remote host is missing an update to netpbm-free announced via advisory USN-665-1.
A security issue affects the following Ubuntu releases:
Ubuntu 6.06 LTS Ubuntu 7.10
This advisory also applies to the corresponding versions of Kubuntu, Edubuntu, and Xubuntu.
Details follow:
It was discovered that Netpbm could be made to overrun a buffer when loading certain images. If a user were tricked into opening a specially crafted GIF image, remote attackers could cause a denial of service or execute arbitrary code with user privileges.
Solution: The problem can be corrected by upgrading your system to the following package versions:
Ubuntu 6.06 LTS: netpbm 2:10.0-10ubuntu1.1
Ubuntu 7.10: netpbm 2:10.0-11ubuntu0.1
In general, a standard system upgrade is sufficient to effect the necessary changes.