static int jpeg2000_decode_packet(Jpeg2000DecoderContext *s,
                                  Jpeg2000CodingStyle *codsty,
                                  Jpeg2000ResLevel *rlevel, int precno,
                                  int layno, uint8_t *expn, int numgbits)
{
    int bandno, cblkno, ret, nb_code_blocks;

    if (!(ret = get_bits(s, 1))) {
        jpeg2000_flush(s);
        return 0;
    } else if (ret < 0)
        return ret;

    for (bandno = 0; bandno < rlevel->nbands; bandno++) {
        Jpeg2000Band *band = rlevel->band + bandno;
        Jpeg2000Prec *prec = band->prec + precno;

        if (band->coord[0][0] == band->coord[0][1] ||
            band->coord[1][0] == band->coord[1][1])
            continue;
        nb_code_blocks =  prec->nb_codeblocks_height *
                          prec->nb_codeblocks_width;
        for (cblkno = 0; cblkno < nb_code_blocks; cblkno++) {
            Jpeg2000Cblk *cblk = prec->cblk + cblkno;
            int incl, newpasses, llen;

            if (cblk->npasses)
                incl = get_bits(s, 1);
            else
                incl = tag_tree_decode(s, prec->cblkincl + cblkno, layno + 1) == layno;
            if (!incl)
                continue;
            else if (incl < 0)
                return incl;

            if (!cblk->npasses) {
                int v = expn[bandno] + numgbits - 1 -
                        tag_tree_decode(s, prec->zerobits + cblkno, 100);
                if (v < 0) {
                    av_log(s->avctx, AV_LOG_ERROR,
                           "nonzerobits %d invalid\n", v);
                    return AVERROR_INVALIDDATA;
                }
                cblk->nonzerobits = v;
            }
            if ((newpasses = getnpasses(s)) < 0)
                return newpasses;
            if ((llen = getlblockinc(s)) < 0)
                return llen;
            cblk->lblock += llen;
            if ((ret = get_bits(s, av_log2(newpasses) + cblk->lblock)) < 0)
                return ret;
            if (ret > sizeof(cblk->data)) {
                avpriv_request_sample(s->avctx,
                                      "Block with lengthinc greater than %zu",
                                      sizeof(cblk->data));
                return AVERROR_PATCHWELCOME;
            }
            cblk->lengthinc = ret;
            cblk->npasses  += newpasses;
        }
    }
    jpeg2000_flush(s);

    if (codsty->csty & JPEG2000_CSTY_EPH) {
        if (bytestream2_peek_be16(&s->g) == JPEG2000_EPH)
            bytestream2_skip(&s->g, 2);
        else
            av_log(s->avctx, AV_LOG_ERROR, "EPH marker not found.\n");
    }

    for (bandno = 0; bandno < rlevel->nbands; bandno++) {
        Jpeg2000Band *band = rlevel->band + bandno;
        Jpeg2000Prec *prec = band->prec + precno;

        nb_code_blocks = prec->nb_codeblocks_height * prec->nb_codeblocks_width;
        for (cblkno = 0; cblkno < nb_code_blocks; cblkno++) {
            Jpeg2000Cblk *cblk = prec->cblk + cblkno;
            if (   bytestream2_get_bytes_left(&s->g) < cblk->lengthinc
                || sizeof(cblk->data) < cblk->length + cblk->lengthinc + 2
            ) {
                av_log(s->avctx, AV_LOG_ERROR,
                       "Block length %d or lengthinc %d is too large\n",
                       cblk->length, cblk->lengthinc);
                return AVERROR_INVALIDDATA;
            }

            bytestream2_get_bufferu(&s->g, cblk->data + cblk->length, cblk->lengthinc);
            cblk->length   += cblk->lengthinc;
            cblk->lengthinc = 0;
        }
    }
    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.