int decode_splitmvs(VP8Context *s, VP56RangeCoder *c, VP8Macroblock *mb,
                    int layout, int is_vp7)
{
    int part_idx;
    int n, num;
    VP8Macroblock *top_mb;
    VP8Macroblock *left_mb = &mb[-1];
    const uint8_t *mbsplits_left = vp8_mbsplits[left_mb->partitioning];
    const uint8_t *mbsplits_top, *mbsplits_cur, *firstidx;
    VP56mv *top_mv;
    VP56mv *left_mv = left_mb->bmv;
    VP56mv *cur_mv  = mb->bmv;

    if (!layout) // layout is inlined, s->mb_layout is not
        top_mb = &mb[2];
    else
        top_mb = &mb[-s->mb_width - 1];
    mbsplits_top = vp8_mbsplits[top_mb->partitioning];
    top_mv       = top_mb->bmv;

    if (vp56_rac_get_prob_branchy(c, vp8_mbsplit_prob[0])) {
        if (vp56_rac_get_prob_branchy(c, vp8_mbsplit_prob[1]))
            part_idx = VP8_SPLITMVMODE_16x8 + vp56_rac_get_prob(c, vp8_mbsplit_prob[2]);
        else
            part_idx = VP8_SPLITMVMODE_8x8;
    } else {
        part_idx = VP8_SPLITMVMODE_4x4;
    }

    num              = vp8_mbsplit_count[part_idx];
    mbsplits_cur     = vp8_mbsplits[part_idx],
    firstidx         = vp8_mbfirstidx[part_idx];
    mb->partitioning = part_idx;

    for (n = 0; n < num; n++) {
        int k = firstidx[n];
        uint32_t left, above;
        const uint8_t *submv_prob;

        if (!(k & 3))
            left = AV_RN32A(&left_mv[mbsplits_left[k + 3]]);
        else
            left = AV_RN32A(&cur_mv[mbsplits_cur[k - 1]]);
        if (k <= 3)
            above = AV_RN32A(&top_mv[mbsplits_top[k + 12]]);
        else
            above = AV_RN32A(&cur_mv[mbsplits_cur[k - 4]]);

        submv_prob = get_submv_prob(left, above, is_vp7);

        if (vp56_rac_get_prob_branchy(c, submv_prob[0])) {
            if (vp56_rac_get_prob_branchy(c, submv_prob[1])) {
                if (vp56_rac_get_prob_branchy(c, submv_prob[2])) {
                    mb->bmv[n].y = mb->mv.y +
                                   read_mv_component(c, s->prob->mvc[0], is_vp7);
                    mb->bmv[n].x = mb->mv.x +
                                   read_mv_component(c, s->prob->mvc[1], is_vp7);
                } else {
                    AV_ZERO32(&mb->bmv[n]);
                }
            } else {
                AV_WN32A(&mb->bmv[n], above);
            }
        } else {
            AV_WN32A(&mb->bmv[n], left);
        }
    }

    return num;
}

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.