Cox played all 16 games for San Francisco last season and was active for two of the 49ers’ three playoff games.
He played nine games this season for the 49ers, with two tackles, before he was released on Nov. 12 when the 49ers activated linebacker Nick Moody.
He subsequently signed with the Seattle Seahawks on Nov. 26, was released the next day, but was re-signed on Dec. 11 after safety Jeron Johnson was injured. He was active for two games, making three tackles.
Cox was released on Friday when Walter Thurmond was activated from a four-game substance-abuse suspension.
Cornerback Carlos Rogers strained his right hamstring on Sunday against the Arizona Cardinals and was scheduled for an MRI today. Cox adds depth to the secondary heading to Green Bay to face the Packers in an NFC Wild Card Playoff on Sunday.
Cox was originally a fifth-round pick of the Denver Broncos out of Oklahoma State in 2010. He was released by Denver before the 2011 season and didn’t play in the NFL that season, signing with the 49ers in March 2012.
He has one career interception in 42 NFL games.