ImageMagick and GraphicsMagick -- DoS via specially crafted PNG file

Kurt Seifried reports:

There is an issue in ImageMagick that is also present in
GraphicsMagick. CVE-2011-3026 deals with libpng memory
allocation, and limitations have been added so that a bad PNG
can’t cause the system to allocate a lot of memory and a
denial of service. However on further investigation of
ImageMagick, Tom Lane found that PNG malloc function
(Magick_png_malloc) in turn calls AcquireMagickMemory with an
improper size argument.