The gdImageCropThreshold function in gd_crop.c in the GD Graphics Library (aka libgd) before 2.2.3, as used in PHP before 7.0.9, allows remote attackers to cause a denial of service (application crash) via an invalid color index. http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-6128
