Air carrier First Officer reported an airspeed exceedance beyond Vmo and altitude deviation caused by severe turbulence.

Narrative

In cruise flight at FL270 we experienced a moment of severe turbulence that occurred for approximately 15 seconds. This severe turbulence caused a deviation of airspeed from a cruise of 290 knots to a sudden rise up to ~315-320 knots. As soon as the airspeed started increasing the captain pulled back the thrust levers to try to stop the increase in speed; but we still received a HIGH SPEED" aural alert. The severe turbulence caused an approximately 30 knot increase; and a slight altitude deviation of approximately 200 feet. The aircraft was only past Vmo for a couple seconds before we managed to reduce the speed and regain control.As PF (Pilot Flying) I should've reacted sooner to the sudden increase in airspeed once the severe turbulence occurred. I didn't fully notice and process the increasing speed until the captain had already pulled the thrust levers back. My hands were immediately on the flight controls in case autopilot had to be turned off and the attitude of the plane needed to be managed. If this situation happens again I will be more prepared to make prompt recoveries in airspeed deviations to help prevent any exceedance of limitations again."