The Black Cats took the lead in the 15th minute when Alex Pritchard scored straight from a corner which went in off the far post.
Cambridge then equalised when Wes Holohan assisted Sam Smith, yet a stunning strike from Nathan Broadhead restored the visitors’ advantage.
Sunderland came under some late pressure in the second half but their defence stood firm.
The result means the Black Cats have closed the gap on some of their promotion rivals.
Our chief Sunderland writer Phil Smith has delivered his verdict on how each player fared at the Abbey Stadium:
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1. Thorben Hoffmann - 7
Perhaps could have done better with the opener, seemingly wrongfooted as Smith went for the near post. Did well in very, very testing second-half conditions. Kept his kicks flat and just about kept a barrage of set pieces out of his goal. 7 Photo: JPI Media
2. Bailey Wright - 8
Superb throughout. Headed dangerous balls away, made some good blocks and made good decisions in possession. 8 Photo: JPI Media
3. Tom Flanagan - 7
A really solid defensive display. Kept it simple in possession and rarely beaten. 7 Photo: JPI Media
4. Callum Doyle - 7
Stepped out really well in the first half and kept it simple in tougher conditions through the second. A solid showing. 7 Photo: Frank Reid