static int mov_read_default(MOVContext *c, AVIOContext *pb, MOVAtom atom)
{
    int64_t total_size = 0;
    MOVAtom a;
    int i;

    if (atom.size < 0)
        atom.size = INT64_MAX;
    while (total_size + 8 <= atom.size && !url_feof(pb)) {
        int (*parse)(MOVContext*, AVIOContext*, MOVAtom) = NULL;
        a.size = atom.size;
        a.type=0;
        if (atom.size >= 8) {
            a.size = avio_rb32(pb);
            a.type = avio_rl32(pb);
            if (atom.type != MKTAG('r','o','o','t') &&
                atom.type != MKTAG('m','o','o','v'))
            {
                if (a.type == MKTAG('t','r','a','k') || a.type == MKTAG('m','d','a','t'))
                {
                    av_log(c->fc, AV_LOG_ERROR, "Broken file, trak/mdat not at top-level\n");
                    avio_skip(pb, -8);
                    return 0;
                }
            }
            total_size += 8;
            if (a.size == 1) { /* 64 bit extended size */
                a.size = avio_rb64(pb) - 8;
                total_size += 8;
            }
        }
        av_dlog(c->fc, "type: %08x '%.4s' parent:'%.4s' sz: %"PRId64" %"PRId64" %"PRId64"\n",
                a.type, (char*)&a.type, (char*)&atom.type, a.size, total_size, atom.size);
        if (a.size == 0) {
            a.size = atom.size - total_size + 8;
        }
        a.size -= 8;
        if (a.size < 0)
            break;
        a.size = FFMIN(a.size, atom.size - total_size);

        for (i = 0; mov_default_parse_table[i].type; i++)
            if (mov_default_parse_table[i].type == a.type) {
                parse = mov_default_parse_table[i].parse;
                break;
            }

        if (!parse && (atom.type == MKTAG('u','d','t','a') ||
                       atom.type == MKTAG('i','l','s','t')))
            parse = mov_read_udta_string;

        if (!parse) { /* skip leaf atoms data */
            avio_skip(pb, a.size);
        } else {
            int64_t start_pos = avio_tell(pb);
            int64_t left;
            int err = parse(c, pb, a);
            if (err < 0)
                return err;
            if (c->found_moov && c->found_mdat &&
                ((!pb->seekable || c->fc->flags & AVFMT_FLAG_IGNIDX) ||
                 start_pos + a.size == avio_size(pb))) {
                if (!pb->seekable || c->fc->flags & AVFMT_FLAG_IGNIDX)
                    c->next_root_atom = start_pos + a.size;
                return 0;
            }
            left = a.size - avio_tell(pb) + start_pos;
            if (left > 0) /* skip garbage at atom end */
                avio_skip(pb, left);
        }

        total_size += a.size;
    }

    if (total_size < atom.size && atom.size < 0x7ffff)
        avio_skip(pb, atom.size - total_size);

    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.