He returns to his former club for an undisclosed fee.
Cardiff have cut their losses on the player who cost aroud £8m in the summer.
Cornelius scored in pre season but was injured in the Capital One Cup game at Accrington. He made several appearances off the bench in the Premier League before starting in the FA Cup at Newcastle and Bolton but was subbed in both games. After 60 mins at Newcastle and after just 45 mins at Bolton.
There were late rumours that Cardiff were trying to get Ross McCormack and Adam Le Fondre last night but the final piece of business was the sale of Cornelius.