Bowler Mitchell Starc helped Australia survive a late scare against Pakistan to go second on the World Cup standings, with a 41-run victory in Taunton.
After a David Warner century helped Australia to 307, Cummins claimed 3/33 with the ball to put the defending champions well on top.
But with Pakistan 160/6, their lower order had other ideas, with first Hasan Ali (32 from) and then Wahab Riaz (45 off 39) putting their team back in the game.
With the equation down to 44 runs off 35 balls and three wickets in hand, Starc (2/43) claimed the wickets of Wahab and Mohammad Amir in the same over to put Australia back in control.
His dismissal of Wahab was, to some degree, fortunate after the Pakistani was given not out to a caught-behind appeal on field, before captain Aaron Finch reviewed with one second left on the countdown clock.
Replays showed the ball had just nipped away from him, brushing the edge of the bat to have him out, before Starc then bowled Amir two balls later.
Glenn Maxwell finished the job, producing an acrobatic run out of Sarfraz Ahmed in the following over to have Pakistan all out for 266.
Cummins had earlier sparked a middle-order collapse, when Pakistan lost 2/24, after being on track at 136/2.
He had Imam-ul-Haq caught down the legside, gloving a ball he attempted to hook, and then got rid of the dangerous Shoaib Malik with a ball that jagged back at him and caught the inside edge on the way to wicketkeeper Alex Carey.
Finch also claimed a rare wicket, as he got through two overs in the absence of the injured Marcus Stoinis, when Mohammad Hafeez swept a ball to Starc on the boundary for 46.
Nathan Coulter-Nile was improved with the ball, but still finished 1/53, while Kane Richardson took 2/62 in his World Cup debut.
The result puts Australia second behind New Zealand, with England and India in third and fourth, but with games in hand.
Australia had earlier appeared to leave the door open for Pakistan, when they fell from 223/2 to all out for 307 in the final 16 overs.
Warner's century marked his first since he returned to the Australian side from his 12-month ban, as he dominated on the drive and punished Pakistan's bowlers whenever they erred in their length.
His 111-ball knock also answered the opener's critics in emphatic fashion, after his slower-than-usual scoring rates had been questioned after the opening three games.
Finch also hit 82 for his sixth straight score above 50 against Pakistan, while the pair's 146-run opening stand was the biggest partnership for any wicket of the tournament.
But after Glenn Maxwell (20) threw his wicket away when he was clean bowled trying to go big, Shaun Marsh (23) and Usman Khawaja (18) both struggled to get going, before falling to left-armer Amir (5/30).
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