One appliance and crew from High Wycombe, one from Beaconsfield and one from Gerrards Cross attended, along with an officer.
One car was well alight when they arrived.
The incident generated multiple calls to Thames Valley Fire Control Service.
The firefighters used two sets of breathing apparatus and one hose reel jet.
Lane one of the motorway and the hard shoulder were closed while they worked at the scene.
National Highways and Thames Valley Police attended.