A bumper assembly includes a bumper beam for absorbing an impact of a vehicle and a crash box attached to the bumper beam and extending along an axis A. A mounting plate is attached to the crash box and defines at least one lateral slot extending laterally along the mounting plate in spaced and perpendicular relationship to the axis A. A fastener extends through the lateral slot for mating with a mounting surface of the vehicle frame to establish a secured position of the bumper assembly. The fastener includes a shoulder disposed in abutting relationship with the mounting surface in the secured position to dispose the mounting plate and the mounting surface in spaced relationship to one another for allowing the fastener to slide laterally along the lateral slot during a vehicle impact to reduce the transfer of lateral impact forces from the bumper assembly to the vehicle frame.