Integer overflow in the _gd2GetHeader function in gd_gd2.c in the GD Graphics Library (aka libgd) before 2.2.3, as used in PHP before 5.5.37, 5.6.x before 5.6.23, and 7.x before 7.0.8, allows remote attackers to cause a denial of service (heap-based buffer overflow and application crash) or possibly have unspecified other impact via crafted chunk dimensions in an image.