static int decode_cblk(Jpeg2000DecoderContext *s, Jpeg2000CodingStyle *codsty,
                       Jpeg2000T1Context *t1, Jpeg2000Cblk *cblk,
                       int width, int height, int bandpos)
{
    int passno = cblk->npasses, pass_t = 2, bpno = cblk->nonzerobits - 1, y;
    int clnpass_cnt = 0;
    int bpass_csty_symbol           = codsty->cblk_style & JPEG2000_CBLK_BYPASS;
    int vert_causal_ctx_csty_symbol = codsty->cblk_style & JPEG2000_CBLK_VSC;

    av_assert0(width  <= JPEG2000_MAX_CBLKW);
    av_assert0(height <= JPEG2000_MAX_CBLKH);

    for (y = 0; y < height; y++)
        memset(t1->data[y], 0, width * sizeof(**t1->data));

    /* If code-block contains no compressed data: nothing to do. */
    if (!cblk->length)
        return 0;

    for (y = 0; y < height + 2; y++)
        memset(t1->flags[y], 0, (width + 2) * sizeof(**t1->flags));

    cblk->data[cblk->length] = 0xff;
    cblk->data[cblk->length+1] = 0xff;
    ff_mqc_initdec(&t1->mqc, cblk->data);

    while (passno--) {
        switch(pass_t) {
        case 0:
            decode_sigpass(t1, width, height, bpno + 1, bandpos,
                           bpass_csty_symbol && (clnpass_cnt >= 4),
                           vert_causal_ctx_csty_symbol);
            break;
        case 1:
            decode_refpass(t1, width, height, bpno + 1);
            if (bpass_csty_symbol && clnpass_cnt >= 4)
                ff_mqc_initdec(&t1->mqc, cblk->data);
            break;
        case 2:
            decode_clnpass(s, t1, width, height, bpno + 1, bandpos,
                           codsty->cblk_style & JPEG2000_CBLK_SEGSYM,
                           vert_causal_ctx_csty_symbol);
            clnpass_cnt = clnpass_cnt + 1;
            if (bpass_csty_symbol && clnpass_cnt >= 4)
                ff_mqc_initdec(&t1->mqc, cblk->data);
            break;
        }

        pass_t++;
        if (pass_t == 3) {
            bpno--;
            pass_t = 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.