Code: tight_detect_smooth_image24(VncState *vs, int w, int h)
{
    int off;
    int x, y, d, dx;
    unsigned int c;
    unsigned int stats[256];
    int pixels = 0;
    int pix, left[3];
    unsigned int errors;
    unsigned char *buf = vs->tight.tight.buffer;

    /*
      * If client is big-endian, color samples begin from the second
      * byte (offset 1) of a 32-bit pixel value.
      */
    off = !!(vs->clientds.flags & QEMU_BIG_ENDIAN_FLAG);
 
     memset(stats, 0, sizeof (stats));
 
    for (y = 0, x = 0; y < h && x < w;) {
        for (d = 0; d < h - y && d < w - x - VNC_TIGHT_DETECT_SUBROW_WIDTH;
             d++) {
            for (c = 0; c < 3; c++) {
                left[c] = buf[((y+d)*w+x+d)*4+off+c] & 0xFF;
            }
            for (dx = 1; dx <= VNC_TIGHT_DETECT_SUBROW_WIDTH; dx++) {
                for (c = 0; c < 3; c++) {
                    pix = buf[((y+d)*w+x+d+dx)*4+off+c] & 0xFF;
                    stats[abs(pix - left[c])]++;
                    left[c] = pix;
                }
                pixels++;
            }
        }
        if (w > h) {
            x += h;
            y = 0;
        } else {
            x = 0;
            y += w;
        }
    }

    /* 95% smooth or more ... */
    if (stats[0] * 33 / pixels >= 95) {
        return 0;
    }

    errors = 0;
    for (c = 1; c < 8; c++) {
        errors += stats[c] * (c * c);
        if (stats[c] == 0 || stats[c] > stats[c-1] * 2) {
            return 0;
        }
    }
    for (; c < 256; c++) {
        errors += stats[c] * (c * c);
    }
    errors /= (pixels * 3 - stats[0]);

    return errors;
}

Vulnerability Type: 
CWE ID: CWE-125
Summary: An out-of-bounds memory access issue was found in Quick Emulator (QEMU) before 1.7.2 in the VNC display driver. This flaw could occur while refreshing the VNC display surface area in the 'vnc_refresh_server_surface'. A user inside a guest could use this flaw to crash the QEMU process.
Commit Message: 