This indicates an attack attempt against a Memory Corruption vulnerability in GraphicsMagick.
The vulnerability is caused by an error when ReadJNGImage and ReadOneJNGImage functions handles a malformed PNG file. A remote attacker may be able to exploit this to execute arbitrary code within the context of the application, via a crafted PNG file.
System Compromise: Remote attacker can gain control of vulnerable systems.
Apply patch, available from the web site.