The Malaysians will face three-time winners Thailand in the two-legged final on Dec. 17 and 20 after one of the biggest Southeast Asian upsets in recent memory.
Dollah Salleh's side scored four times in the first half against the heavily favoured 2008 champions who were playing before a packed house in Hanoi.
Vietnam had the advantage of two away goals going into the second leg at the My Dinh Stadium, having won 2-1 at Shah Alam last Sunday. But they were wary of the unpredictable Malaysians who defied predictions by upsetting the other host nation, Singapore, in their final group match to qualify for the knockout stages.
Toshiya Miura's side, the Group A winners, went into the game with an unbeaten record in the 2014 tournament, with three wins and one draw.
But within five minutes, the Suzuki Cup favourites found themselves behind. After Indra Putra Mahayuddin broke clear in the box, he was hacked down by Ngoc Hai Que, who was shown a yellow card. Captain Safiq Rahim converted the spot kick after it was re-taken after encroachment on the first attempt.
