@@ -469,9 +469,15 @@ static int shorten_decode_frame(AVCodecContext *avctx,

             case FN_BITSHIFT:

                 s->bitshift = get_ur_golomb_shorten(&s->gb, BITSHIFTSIZE);

                 break;

-            case FN_BLOCKSIZE:

-                s->blocksize = get_uint(s, av_log2(s->blocksize));

+            case FN_BLOCKSIZE: {

+                int blocksize = get_uint(s, av_log2(s->blocksize));

+                if (blocksize > s->blocksize) {

+                    av_log(avctx, AV_LOG_ERROR, "Increasing block size is not supported\n");

+                    return AVERROR_PATCHWELCOME;

+                }

+                s->blocksize = blocksize;

                 break;

+            }

             case FN_QUIT:

                 *data_size = 0;

                 return buf_size;