Why is my 2010 Chevy Malibu third brake light not working?

Has Your brake light on Your 2010 Chevrolet Malibu failed completely, or intermittently Is it also consistent with the gear shift not moving out of park In the latter case, there's a small sensor on Your brake pedal, that engages the light, as well as lets You shift. If this has started to fail, You'll encounter the issue You've described. If the brake light isn't working at all, and You've already checked the lightbulb, the next thing to look at is the fuse to the light. After that, You're going to want to verify the wiring hasn't become compromised, by rodents or careless home mechanics. If You've still had no luck, there could be a more serious issue, which is likely going to require You bringing it in to a shop.