While standing on campfire, I don't burn

What do you mean with "I don't burn"? You don't take any damage? Or your player model isn't on fire?

Yes, I do take damage but my player model is not on fire.

this also happens with magma blocks

Both campfires and magma blocks deal fire damage, but they are not supposed to set the player on fire. This would be a feature request, not a bug.