In GraphicsMagick 1.4 snapshot-20171217 Q8, there is a heap-based buffer over-read in ReadMNGImage in coders/png.c, related to accessing one byte before testing whether a limit has been reached.Referenceshttps://sourceforge.net/p/graphicsmagick/bugs/535/https://www.debian.org/security/2018/dsa-4321https://lists.debian.org/debian-lts-announce/2018/06/msg00009.htmlhttp://hg.graphicsmagick.org/hg/GraphicsMagick/rev/1721f1b7e67ahttps://lists.debian.org/debian-lts-announce/2018/01/msg00005.htmlhttps://usn.ubuntu.com/4266-1/
