gd: incorrect boundary adjustment in _gdContributionsCalc

gdinterpolation.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...