In ImageMagick before 6.9.9-1 and 7.x before 7.0.6-2, the ReadOnePNGImage function in coders/png.c allows remote attackers to cause a denial of service (application hang in LockSemaphoreInfo) via a PNG file with a width equal to MAGICK_WIDTH_LIMIT.
https://www.debian.org/security/2017/dsa-4019
https://security.gentoo.org/glsa/201711-07
https://github.com/ImageMagick/ImageMagick/issues/596