What is the ruling on buying a car through Murabaha from a usurious bank, when one is not certain about the bank's ownership of the car?

The correct Murabaha involves the bank purchasing the car, acquiring ownership and liability for it, and then selling it to the customer. However, if banks purchase directly for the customer without the commodity entering their possession, this is an impermissible usurious loan, because contracts are judged by their meanings. If the bank owns the car and sells it to you without stipulating a penalty for late payment, then there is no harm in that.