ReadOneJNGImage in coders/png.c in GraphicsMagick 1.3.26 has a use-after-free issue when the height or width is zero, related to ReadJNGImage.
https://www.debian.org/security/2018/dsa-4321
https://sourceforge.net/p/graphicsmagick/bugs/469/
http://hg.graphicsmagick.org/hg/GraphicsMagick?cmd=changeset%3Bnode=df946910910d
http://hg.graphicsmagick.org/hg/GraphicsMagick?cmd=changeset%3Bnode=93bdb9b30076