From changelog:
Integer Overflow in gdImagePaletteToTrueColor() resulting in heap overflow (CVE-2016-5767)
=> already in 2.1.1
Integer Overflow in _gd2GetHeader() resulting in heap overflow (CVE-2016-5766)
=> seems missing in libgd compared to PHP
=> under investigation
NULL Pointer Dereference at _gdScaleVert
=> unneeded, already on 2.1.1