A cargo door lock for securing the rear doors of containers such as the rear doors of a tractor-trailer container, a sea-rail container, or a static container. The cargo door lock attaches to vertical rods to prevent unauthorized opening of the container rear doors. The cargo door lock includes an extendable shaft with first and second opposite ends, first and second securing hooks that are respectively attached to the first and second opposite ends, and a lock mechanism. The lock mechanism is set at a perpendicular angle with respect to the first and second securing hooks.