Scunthorpe's Cleveland Taylor struck twice in three minutes to put his side back in the automatic promotion places and send Cambridge closer to the drop.
Scunthorpe took a fortunate lead when Richard Kell squeezed the ball under Everton-bound John Ruddy.

Andy Crosby flicked home a Peter Beagrie corner to double the lead.

Taylor came off the bench on 65 minutes and made it three with a fine low drive from 25 yards before cracking home a Beagrie cross to complete the scoring.