This is one of big problems with the software industry nowadays. It has a role to play in nearly every major industry but does not have the same regulatory hoops to jump through to get into that industry. In this case, I am sure multiple mechanical and electrical licensed professional engineers had to stamp all of the physical components that make up the vehicle but I would be very surprised if any software was ever signed off on by a licensed professional engineer explicitly (there is a case to be made for implied acceptance by the engineer of record for the system that the software runs on but I think it is weak).
It will be interesting to watch the ongoing situation with Chrysler:
http://www.wired.com/2015/08/chrysler-harman-hit-class-actio...
If the class action goes forward there will be a legal examination of whether a security flaw that allows remote tampering is a safety defect or not (of course it is, but I mean in the context of liability).
I pretty much expect that automakers will quickly start shipping systems with effective segregation (the cost pretty clearly doesn't outweigh the PR downside), so the interesting question really is whether the cars on the road today represent negligence or not.
I suspect whole auto industry needs to re-learn (if they ever learned in the first place) the lesson of the Therac-25 and what "fail safe" means. Some dangerous situations should not be possible.
Unfortunately, I suspect the auto industry will choose to learn those lessons the hard way. When people die from someone messing with their steering or brakes remotely, I hope whomever signed off the idea of mixing remote signalling with critical systems is found personally liable for manslaughter.