This vulnerability affects all vehicles regardless of the brand. Thieves can use a simple device to open your car and steal everything in it or even drive your car away while you're sleeping, at work, in restaurant or shopping.
Keyless car entry allows the key holder to open and start the car without pressing any button on the key fob, just by having it in his pocket. Once you touch the door handle, communication between the car and the key is triggered (by proximity sensor or a button depending on your car). When the key receives the signal (similar short-distance type of communication as NFC) and it matches the stored pairing algorythm, they key sends long-distance command to open the car (same as if you press the fob button).
Normally, this works for distance of less than 1 meter only. By using simple and cheap (under $100) amplifier, thieves can amplify the car signal and reach the key in distance of 30m or more. It in fact means that when the thief with an amplifier comes to your car and touch the handle, your key fob lying inside your house while you are sleeping or in your pocket while having lunch will respond and unlock the car the same way as if you do it yourself. Whatsmore, the thief can lock the car after stealing your items so there will be no traces of robbery thus make it hard to get paid by insurrance company for the stolen items.
There is even more sophisticated approach that allows thieves to open and start your car by a distance of several hundreds meters. Thieves operate in pairs - first thief move next to the wall of your house or follow you into a store to be close to your fob signal. He uses a device that amplifies and relays the signal to an accomplice who is standing next to your car with another device. Your car thinks your fob is next to the car so the doors unlock instantly. If the car has push button start, thiefs can start and drive the car away until they turn the engine off.