Alexander spent the first four years of his career with the Vikings.
The 26-year-old cornerback was also released from jail after posting bond.
Alexander left the Bengals after his father went missing in Florida.
With the Vikings pressed against the cap, change could be coming in Minnesota.
The 41-year old hasn't played since the 2017 season.
The fourth-year cornerback has one interception this season.
The pressure is now on Xavier Rhodes and Trae Waynes.