In a frantic finish Cambridge grabbed two late goals in a minute, which they thought had beaten their Wrexham bogey, but then conceded an equaliser in the fourth minute of stoppage time.
It all boiled down to a result which reflected a match in which Cambridge fought back in the second half after sleep-walking their way through the first.
It looked as though they might end Wrexham's four-match winning run at the Abbey Stadium when Tom Youngs and Omer Riza struck in the 84th and 85th minutes.
But a lack of concentration at a corner kick with seconds to go allowed Craig Morgan to head the ball under the crossbar.
Cambridge boss John Taylor was so disgusted by the defensive lapse he sent his coach Dale Brooks out to comment.
Said Brooks: "There's no excuse for giving away a goal like that at that stage.
"We recovered after an awful first half, missed a few chances but then looked like getting the points due to some sharp finishing. In the end it was a big disappointment."
That was also how Wrexham manager Denis Smith felt. He said: "The equaliser couldn't have come much later, but I thought we more than deserved it after dominating the first half and defending so well in the second.
"We lost two key defenders goalkeeper Andy Dibble and centre-back Dennis Lawrence to injury in the last quarter of an hour and that let Cambridge in."
Jim Whitley fired Wrexham in front in the 26th minute with a blistering 25-yard drive and Cambridge hardly featured as an attacking force.
But the home side took over early in the second period creating chances for Dave Kitson, whose shot was well saved by Dibble and Youngs who headed over before Youngs and Riza took advantage of the reorganised defence to score their goals within a minute of each other