static int flashsv_decode_block(AVCodecContext *avctx, AVPacket *avpkt,
                                GetBitContext *gb, int block_size,
                                int width, int height, int x_pos, int y_pos,
                                int blk_idx)
{
    struct FlashSVContext *s = avctx->priv_data;
    uint8_t *line = s->tmpblock;
    int k;
    int ret = inflateReset(&s->zstream);
    if (ret != Z_OK) {
        av_log(avctx, AV_LOG_ERROR, "Inflate reset error: %d\n", ret);
        return AVERROR_UNKNOWN;
    }
    if (s->zlibprime_curr || s->zlibprime_prev) {
        ret = flashsv2_prime(s,
                             s->blocks[blk_idx].pos,
                             s->blocks[blk_idx].size);
        if (ret < 0)
            return ret;
    }
    s->zstream.next_in   = avpkt->data + get_bits_count(gb) / 8;
    s->zstream.avail_in  = block_size;
    s->zstream.next_out  = s->tmpblock;
    s->zstream.avail_out = s->block_size * 3;
    ret = inflate(&s->zstream, Z_FINISH);
    if (ret == Z_DATA_ERROR) {
        av_log(avctx, AV_LOG_ERROR, "Zlib resync occurred\n");
        inflateSync(&s->zstream);
        ret = inflate(&s->zstream, Z_FINISH);
    }

    if (ret != Z_OK && ret != Z_STREAM_END) {
    }

    if (s->is_keyframe) {
        s->blocks[blk_idx].pos      = s->keyframedata + (get_bits_count(gb) / 8);
        s->blocks[blk_idx].size     = block_size;
    }
    if (!s->color_depth) {
        /* Flash Screen Video stores the image upside down, so copy
         * lines to destination in reverse order. */
        for (k = 1; k <= s->diff_height; k++) {
            memcpy(s->frame.data[0] + x_pos * 3 +
                   (s->image_height - y_pos - s->diff_start - k) * s->frame.linesize[0],
                   line, width * 3);
            /* advance source pointer to next line */
            line += width * 3;
        }
    } else {
        /* hybrid 15-bit/palette mode */
        decode_hybrid(s->tmpblock, s->frame.data[0],
                      s->image_height - (y_pos + 1 + s->diff_start + s->diff_height),
                      x_pos, s->diff_height, width,
                      s->frame.linesize[0], s->pal);
    }
    skip_bits_long(gb, 8 * block_size); /* skip the consumed bits */
    return 0;
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.