static int decode_unit(SCPRContext *s, PixelModel *pixel, unsigned step, unsigned *rval)
{
    GetByteContext *gb = &s->gb;
    RangeCoder *rc = &s->rc;
    unsigned totfr = pixel->total_freq;
    unsigned value, x = 0, cumfr = 0, cnt_x = 0;
    int i, j, ret, c, cnt_c;

    if ((ret = s->get_freq(rc, totfr, &value)) < 0)
        return ret;

    while (x < 16) {
        cnt_x = pixel->lookup[x];
        if (value >= cumfr + cnt_x)
            cumfr += cnt_x;
        else
            break;
        x++;
    }

    c = x * 16;
    cnt_c = 0;
    while (c < 256) {
        cnt_c = pixel->freq[c];
        if (value >= cumfr + cnt_c)
            cumfr += cnt_c;
        else
             break;
         c++;
     }
    if (x >= 16 || c >= 256) {
        return AVERROR_INVALIDDATA;
    }
 
     if ((ret = s->decode(gb, rc, cumfr, cnt_c, totfr)) < 0)
         return ret;

    pixel->freq[c] = cnt_c + step;
    pixel->lookup[x] = cnt_x + step;
    totfr += step;
    if (totfr > BOT) {
        totfr = 0;
        for (i = 0; i < 256; i++) {
            unsigned nc = (pixel->freq[i] >> 1) + 1;
            pixel->freq[i] = nc;
            totfr += nc;
        }
        for (i = 0; i < 16; i++) {
            unsigned sum = 0;
            unsigned i16_17 = i << 4;
            for (j = 0; j < 16; j++)
                sum += pixel->freq[i16_17 + j];
            pixel->lookup[i] = sum;
        }
    }
    pixel->total_freq = totfr;

    *rval = c & s->cbits;

    return 0;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.