The Giants were granted a roster exemption for Kennedy through Nov. 21.
Kennedy was suspended for violating the NFL performance-enhancing drug policy, according to a league source.
It's unclear what substance Kennedy took to trigger the punishment from the league.
Kennedy is a former St. Louis Rams first-round draft pick and has previous stints with the Chicago Bears, Jacksonville Jaguars and the Minnesota Vikings.
He joined the Giants on a one-year deal in August.
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Source: Jimmy Kennedy reinstated
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