Endeavor Air flight 4985 encountered severe turbulence while descending through 17,400 feet to Cincinnati Northern Kentucky International Airport (CVG), after which a passenger reported a serious injury after seeking follow-up medical care. The flight crew reported that the fasten seat belt sign was illuminated, and a public address (PA) announcement had been made instructing passengers to fasten their seat belts and remain seated. As the aircraft descended through about 17,400 feet, the pilots observed a cumulus cloud directly ahead that had not been displayed on the airplane’s weather radar as moderate or severe returns. The captain reduced the descent rate and continued through the top of the cloud, when the aircraft encountered severe turbulence. At the time of the turbulence encounter, the two flight attendants (FAs) were conducting final cabin safety checks. During the event, both FAs were lifted into the air and thrown to the floor, with one FA striking their head on the ceiling of the aircraft. Following the turbulence, both FAs returned to their assigned jump seats and secured their safety harnesses, while checking on passengers. A public address (PA) announcement was made instructing passengers to “please take your seat and fasten your seatbelt,” followed by a second announcement advising passengers to press their call button if they required assistance. Two passengers activated their call buttons and reported striking their heads on the ceiling during the turbulence encounter. Upon arrival at the gate, medical personnel met the aircraft. After evaluation, both passengers were released. Endeavor Air received an unverified report following the flight that one passenger sought further medical treatment and was subsequently diagnosed with a serious injury. At the time of the turbulence encounter there was no active significant meteorological information (SIGMETs), convective SIGMETs, airman’s meteorological information (AIRMETs), or pilot reports (PIREPs) of any significant turbulence.