U's boss John Taylor made his move for the 19-year-old after Franco Nacca injured an ankle which will sideline him for several weeks.

McCafferty is yet to figure in the Premiership for Charlton but has been a regular at reserve-team level.

"He's not the biggest, but he's got good feet and a good engine and he uses the ball well," Taylor told Cambridge's website.

"Obviously with Franco's injury we had to look at bringing someone in and we've had him in our minds for a little while so we're bringing him in and giving him the chance of some football."