The Canadiens scored to cut the Maple Leafs' lead to 4-3 late in the second period.
The officials reviewed the play and upheld the goal, but the Maple Leafs then used a coach's challenge, claiming there had been goaltender interference. Montreal forward Jesperi Kotkaniemi appeared to push Toronto goaltender Frederik Andersen's pad into the net along with the puck.
The goal was reviewed for a second time, and the league overturned the initial call.
The NHL later issued an explanation but only referenced the goaltender interference challenge, saying it wiped out the goal because Kotkaniemi did indeed push Andersen's pad.
Kotkaniemi scored earlier in the second period to cut the Maple Leafs' lead to 2-1.
The Maple Leafs defeated the Canadiens 5-3, thanks in large part to Auston Matthews, who racked up two goals and two assists.