Exum, 26, is a former sixth-round pick by the Vikings in the 2014 NFL Draft. He was entering the final year of a four-year, $2,335,788 rookie contract and was set to make a base salary of $690,000 for the 2017 season when the team waived him.
Exum landed on Minnesota’s injured reserve in 2015 with injuries to his ribs and hips, while he missed all of last year with a leg injury.
The Bills brought him in for a workout last month but did not sign him to a contract.
In 2015, Exum appeared in 12 games and recorded 13 tackles, two fumble recoveries and a forced fumble for the Vikings.