Integer signedness error in the dynamicGetbuf function in gd_io_dp.c in the GD Graphics Library (aka libgd) through 2.2.3, as used in PHP before 5.6.28 and 7.x before 7.0.13, allows remote attackers to cause a denial of service (stack-based buffer overflow) or possibly have unspecified other impact via a crafted imagecreatefromstring call.