In ImageMagick 7.0.6-3, a missing NULL assignment was found in coders/png.c, leading to an invalid free in the function RelinquishMagickMemory in MagickCore/memory.c, which allows attackers to cause a denial of service.Referenceshttps://github.com/ImageMagick/ImageMagick/issues/621https://www.debian.org/security/2017/dsa-4019
