The England international struck amid a goalmouth scramble as the Black Cats launched one final attack at the Stadium of Light on Saturday evening.
Until that point, it looked as though Cesc Fabregas' freak goal would be enough to hand the visitors a hard-fought win.
The Spaniard's 13th-minute block sent Anton Ferdinand's attempted clearance sailing over the head of stranded goalkeeper Simon Mignolet and into the net.
But the Gunners had only themselves to blame after having midfielder Alex Song sent off for a second bookable offence 10 minutes after the break, while substitute Tomas Rosicky skied a 74th-minute penalty wastefully over the bar.
Sunderland have fared well against the Premier League's big boys in recent times, and claimed the scalp of big-spending Manchester City in their last outing at the Stadium of Light.
But manager Steve Bruce knew that if they were to get the better of the Gunners as they did last season, they would have to be at their best and probably enjoy some good fortune.
He could have no quibbles with their first-half display as they more than made a fight of it against a side who had scored six without reply in the Champions League in midweek.
However, what luck came their way was of the sickeningly bad variety.
The game was 13 minutes old when Fabregas closed down central defender Ferdinand as he prepared to clear.
But even he could not believe his eyes when the ball cannoned back off him and looped in a perfect arc over astonished Mignolet, who was far enough off his line for it to evade him and drop into the empty net.
Bruce's men might have been back on level terms within two minutes when Nedum Onuoha met Jordan Henderson's corner unopposed, but powered his header high over Manuel Almunia's crossbar.
Mignolet had to produce solid saves to deny first Song and then Andrey Arshavin as the Gunners looked to kill the game off, and his team-mates stepped up a gear in the search for an equaliser.
With Henderson and Steed Malbranque harrying in the middle of the field, the visitors were unable to settle into their renowned passing game on a sustained basis, although the service to lone frontman Bent was too often short of the required quality.
However, summer singing Cristian Riveros might have levelled eight minutes before the break when he met Ahmed Elmohamady's cross with a diving header, but under pressure from Bacary Sagna, could not direct his effort on goal.
Gunners boss Arsene Wenger found himself in the headlines once again this week after calling for greater protection for his players, although it was the Gunners who picked up the first half's only two bookings with Jack Wilshere and Song both transgressing once too often for referee Phil Dowd.
Danny Welbeck smashed a first-time shot just wide within seconds of the restart, but it was Arsenal who looked the more threatening as the second half unfolded.
Arshavin clipped a 47th-minute Marouane Chamakh cross over the bar and then squandered a gilt-edged chance after Song had picked him out, and Chamakh could not beat Mignolet one on one after being set up by Samir Nasri's fine 52nd-minute pass.
But Sunderland got a break three minutes later when Song, who had been cautioned for a foul on Henderson before the break, picked up a second booking for a challenge on Malbranque and was dismissed.
The home side perhaps should have made their numerical advantage count within three minutes when Henderson squared for Bent inside the penalty area, but he shot uncharacteristically high and wide.
Bruce sent on record signing Asamoah Gyan for Riveros with 26 minutes remaining, but it was the Gunners who went close when Rosicky shot just wide six minutes later at the end of a flowing move.
The Czech should have wrapped up the victory with 16 minutes to play when Elmohamady tripped Nasri inside the box and Mr Dowd pointed to the spot.
However, Rosicky blazed high over from 12 yards to keep Sunderland's hopes alive.
Gyan glanced an 81st-minute header straight at Almunia, who had to get down well to claim Henderson's last-minute half-volley, but salvation arrived deep into added time when Gael Clichy's clearance dropped perfectly for Bent to smash it home from close range.