Ovono, who has been without a club since leaving Le Mans at the end of last season, will stay at Sochaux until next June.
Cros tore ligaments in his knee in a League Cup game against St Etienne on October 30.
Ovono has been included in the squad to travel to Ajaccio in Ligue 1 in Saturday.
Sochaux are third from bottom after 12 games.
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