Can break furnace by hand without any effects or tools

This bug is not very big and you can fix it easily. I will try my best to speak it easily.

The bug is: You can break a furnace (normal furnace) by a empty hand. And I don't have any tools like pickaxe or any effects like haste. It takes me 17.5 seconds to break it, but it loot a furnace.

Please fix it!