Mansfield made it 16 goals from their last three home games as they beat Cambridge 3-1.
The Stags maintained their play-off push with a fifth win in six matches, while United suffered a third defeat on the bounce.
Lee Stevenson put the finishing touches on a goalmouth scramble to put the hosts ahead after 11 minutes.
The visitors drew level when Liam Hughes headed in from a Rossi Jarvis corner with 31 minutes gone.
But Paul Cox's men regained the lead just before half time when the U's switched off at a corner to allow Luke Jones to poke home from close range.
Defender Colin Daniel added the third from inside the box after 71 minutes to crown a swift passing move from the rampant home side.