Redding's pick and Cundiff's kick with 9 seconds left -- his second of the fourth quarter and third of the game -- handed the fourth win in five contests to the Ravens (10-4).
Joe Flacco went 10-of-20 through the air for 172 yards and two touchdowns for Baltimore. Five of the completions went to Ray Rice for 80 yards, and Rice also racked up for 153 yards and a TD on the ground.
Drew Brees passed for 267 yards and trio of scoring strikes for the Saints (10-4), whose six-game winning streak was snapped.
Two TD passes went to Jimmy Graham and Marques Colston added 80 yards on six catches in the loss.