Limit length of bulk string to 4MB. That should really be enough for a Minetest block.

parser.go

@@ -92,6 +92,10 @@ func (rp *RedisParser) bulkString(line []byte) bool {
 	case i == 0:
 		return rp.consumer.ConsumeBulkString([]byte{})
 	default:
+		if i >= 4*1024*1024 { // 4MB should be sufficient
+			return rp.consumer.ConsumeError(
+				fmt.Errorf("Bulk string too large (%d bytes).\n", i))
+		}
 		data := make([]byte, i, i)
 		for rest := i; rest > 0; {
 			var n int