Corey Perry had a goal and an assist, and Allen made 23 saves for Montreal (10-6-6), which is 1-1-2 since Dominique Ducharme took over as coach after Claude Julien was fired Feb. 24.
The Jets, who are 5-0 this season in games decided in overtime, did not have a defenseman on the ice when Dubois scored.
"Everybody's man-on-man, so if you've got two forwards and a defenseman both of those forwards are doing the same thing that if there's three forwards on the ice," Jets coach Paul Maurice said. "But if you look at the roster at the end of the year the guys who score all the goals are forwards. So we'll try to put as many forwards on the ice as we can."
The Canadiens, who also tried using three forwards 3-on-3, have lost all six games that have gone to overtime, including two shootout losses.
"I mean obviously we're trying to score goals and we had some good looks, some good opportunities," said Montreal forward Tyler Toffoli, who scored his 14th goal. "But we've just got to find a way to win some of these games in overtime here."
Canadiens captain Shea Weber said, "I think we're doing some good things, it's not all bad. We're playing a pretty sound game for the most part. Obviously there's a couple mistakes there. Mistakes are going to happen in games and you want to limit those mistakes, obviously, and especially early. We didn't get off to a really good start and Jake really saved our you-know-what at the start. He made a couple huge saves and let us settle in."
The Canadiens close out a three-game homestand Saturday in the second of a two-game set against the Jets, who began a five-game road trip.
"Our players showed a lot of character tonight," Ducharme said. "The things we didn't do well are easy enough to fix."