It seemed the teams were about to go into overtime when New York's Hakeem Nicks made his second touchdown grab of the day with 58 seconds left and D.J. Ware bulled his way into the end zone on a 2-point conversion to produce a 35-35 tie.
But Aaron Rodgers (28-of-46, 369 yards, four touchdowns) took over and drove the Packers 68 yards on four straight completions to get within range for Crosby.
The 12-0 Packers' victory was a franchise-record 18th straight dating back to last year and marked the best start to a season in team history.
Eli Manning completed 23-of-40 passes for 347 yards, three touchdowns and an interception for the Giants (6-6), who lost their fourth straight.