gd_interpolation.c in the GD Graphics Library (aka libgd) before 2.1.1 as used in PHP before 5.5.36 5.6.x before 5.6.22 and 7.x before 7.0.7 allows remote attackers to cause a denial of service (out-of-bounds read) or possibly have unspecified other impact via a crafted image that is mishandled by the imagescale function.