The loss was the sixth straight for Washington State (2-7, 0-6 Pac-12), assuring coach Mike Leach of his first losing season.
Utah (4-5, 2-4) has won two straight.
White also caught an 18-yard TD pass as Utah scored on five first-half possessions and led 31-0 at halftime.
Dunn opened the second half with his school-record fourth career 100-yard return. He had an NCAA-record two 100-yard kickoff returns last week.
Utah freshman Travis Wilson completed 17 of 21 passes for 171 yards, with two touchdowns and an interception.
Washington State's Jeff Tuel was 23 of 45 for 232 yards, with a 5-yard TD pass to Kristoff Williams on the game's final play. Tuel was intercepted, fumbled and sacked six times.
The Utes are 11-0 when White rushes for 100 yards. He had 96 by halftime, and carried the ball just three times in the second half before taking a seat in the blowout victory.
White's 47-yard run around right end gave Utah a 7-0 lead with 9:04 left in the first quarter. He broke two tackles on the play, including one at the 30-yard line that gave him a clear path down the sideline.
Utah took a 14-0 lead on Wilson's 5-yard TD pass to Max Moala with 3:46 left in the first. The big play in the drive was Wilson's 24-yard pass across the middle to Anthony Denham, who held on despite a high hit by Casey Locker that knocked Denham's helmet off and drew a 15-yard personal-foul penalty.
White's 2-yard touchdown run pushed Utah's lead to 21-0 with 12:07 left in the half. Four minutes later, Utah led 24-0 after Reggie Topps' interception set up Coleman Petersen's 20-yard field goal - his first in six games. Wilson's 18-yard TD pass to White gave Utah a 31-0 lead at the break.
At halftime, Utah held a 285-116 edge in total yards, 141-15 edge in rushing yards and 7-minute edge in time of possession.
Nothing went right for the Cougars and Tuel, who set a school passing mark with 43 completions last week as Washington State took it down to the wire against nationally ranked Stanford.
Tuel completed three of his first five passes for 41 yards Saturday, but was just 1 of 9 for 6 yards the rest of the quarter.
Washington State crossed midfield three times in the first half, with one possession ending on a missed 49-yard field goal by Andrew Furney and two failed fourth-down plays. Tuel threw behind Marquess Wilson on fourth-and-12 from the Utah 37. And on fourth-and-1 from the Utes' 34, Trevor Reilly batted down his pass at the line.
Leach pulled Tuel in the third quarter and inserted Connor Halliday, but Tuel finished the game, engineering the late TD drive to avoid a shutout.
The Utes dominated on defense despite missing top cornerback Ryan Lacy, who did not dress because of an undisclosed injury.
The Cougars started 0 for 9 on third-down conversions and 0 for 2 on fourth down.
Utah held a 453-255 advantage in total yards, limiting the nation's 120th-ranked rushing attack to minus-4 yards.
Marquess Wilson entered the game with 184 career receptions and needed 12 to set the school record of 195. He finished with five catches for 73 yards.