Today we received a report from Marco Grassi about a heap overflow
in the 8BIM reader. 8BIM is a metadata chunk often attached to JPEG files.

After investigation it was found that there was a small unsigned overflow
leading to a huge size value, which then resulted in a heap overflow
(causing a crash).

We believe that this issue exists in all GraphicsMagick
releases to date (including 1.3.25).