I have so far only seen the various car networks compromised through physical access to the vehicles diagnosis ports. It's safe to say all bets are off once you

I have so far only seen the various car networks compromised through physical access to the vehicles diagnosis ports. It's safe to say all bets are off once you start plugging physical things into the car. Doesn't mean a head unit couldn't be compromised and start flooding the specific can bus its sitting on with packets, but usually head units are treated with a bit more care than the rest of the cars networks. Trying to jump can networks through one of the gateways, I don't think would be an easy task either.