United pulled one back early in the second half through Paul McShane but Malcolm Christie restored the two goal cushion from the penalty spot with less than 20 minutes remaining.
As the game entered the dying minutes United shocked Boro with two late goals, from Sylvan Ebanks-Blake, to earn an undeserved draw.
Boro team: Turnbull, McMahon, Taylor, Kennedy, Bates, Wheater, Reed, Peacock, Christie, Graham (Hines 61), Johnson (Grounds 83).
Unused subs: Knight, Poole, Collett.