Code: static inline LineContribType *_gdContributionsCalc(unsigned int line_size, unsigned int src_size, double scale_d,  const interpolation_method pFilter)
{
    double width_d;
    double scale_f_d = 1.0;
    const double filter_width_d = DEFAULT_BOX_RADIUS;
	int windows_size;
	unsigned int u;
	LineContribType *res;

    if (scale_d < 1.0) {
        width_d = filter_width_d / scale_d;
        scale_f_d = scale_d;
    }  else {
        width_d= filter_width_d;
    }

    windows_size = 2 * (int)ceil(width_d) + 1;
    res = _gdContributionsAlloc(line_size, windows_size);

    for (u = 0; u < line_size; u++) {
        const double dCenter = (double)u / scale_d;
        /* get the significant edge points affecting the pixel */
        register int iLeft = MAX(0, (int)floor (dCenter - width_d));
        int iRight = MIN((int)ceil(dCenter + width_d), (int)src_size - 1);
         double dTotalWeight = 0.0;
 		int iSrc;
 
        res->ContribRow[u].Left = iLeft;
        res->ContribRow[u].Right = iRight;
         /* Cut edge points to fit in filter window in case of spill-off */
         if (iRight - iLeft + 1 > windows_size)  {
             if (iLeft < ((int)src_size - 1 / 2))  {
                iLeft++;
            } else {
                iRight--;
             }
         }
 
         for (iSrc = iLeft; iSrc <= iRight; iSrc++) {
             dTotalWeight += (res->ContribRow[u].Weights[iSrc-iLeft] =  scale_f_d * (*pFilter)(scale_f_d * (dCenter - (double)iSrc)));
         }

		if (dTotalWeight < 0.0) {
			_gdContributionsFree(res);
			return NULL;
		}

        if (dTotalWeight > 0.0) {
            for (iSrc = iLeft; iSrc <= iRight; iSrc++) {
                res->ContribRow[u].Weights[iSrc-iLeft] /= dTotalWeight;
            }
        }
   }
   return res;
}

Vulnerability Type: DoS 
CWE ID: CWE-125
Summary: 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.
Commit Message: Fixed bug #72227: imagescale out-of-bounds read

Ported from https://github.com/libgd/libgd/commit/4f65a3e4eedaffa1efcf9ee1eb08f0b504fbc31a