The remote host is missing an update to the system as announced in the referenced advisory.
The following packages are affected: linux-png png
CVE-2004-0421 The Portable Network Graphics library (libpng) 1.0.15 and earlier allows attackers to cause a denial of service (crash) via a malformed PNG image file that triggers an error that causes an out-of-bounds read when creating the error message.
Solution: Update your system with the appropriate patches or software upgrades.