Kidderminster Harriers climbed into the Blue Square Bet Premier play-off zone as they made it four league wins in a row at the Abbey Stadium.
Harriers striker Sean Canham fired home a low shot from the edge of the box to register his first goal for the club three minutes before the break.
Adam Marriott's free-kick levelled for Cambridge a minute into injury time.
But there was one last final twist as substitute Jamille Matt headed home to put Harriers back in front.
Cambridge almost opened the scoring with the very first attack, but Conal Platt's 20-yard shot was superbly parried around the post by visiting keeper Daniel Lewis.
Canham's opener was due reward for the way Steve Burr's spirited Harriers got back in the game.
And it seemed as if their night would be ruined when Marriott struck home from 25 yards.
But Harriers went straight back up the other end to win it when Matt, on as an 86th minute sub for Canham, nodded home Matty Blair's cross.
The defeat heaps more misery on Cambridge, who have slid to 17th thanks to their winless run of eight league games.
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