Cammalleri scored during a 5-on-3 Montreal power play midway through the first period and helped out on Brian Gionta's go-ahead tally 5:48 into the middle frame, which also came as the Habs were skating with a two-man advantage.
Carey Price stopped 31-of-32 shots, including 11 in the third period, as Montreal avoided elimination and knotted their Eastern Conference quarterfinal series at 3-3.
Dennis Seidenberg found the net for the Bruins, who will host the decisive contest Wednesday in Boston.
Tim Thomas made 25 saves for Boston.
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