I just bought a CX-50 after my CX-5 was totaled in a car accident but I believe the oil control valve gasket needs to be replaced. This is something that can happen. I replaced the valve cover gasket myself because I had some minor oil leaks going into my spark plugs. It involves taking the whole cover off, so if this isn't something you want to do, have the dealer or a mechanic change the gasket for you. However, if you have the tools, I'd recommend just doing it yourself.
Mazda247 forums have a great guide on it from user felixd but unfortunately it won't let met post links.