IFAB: VAR will be able to hand out retrospective red cards

The International Football Association Board (IFAB) confirmed that the VAR can inform the referee of off-the-ball incidents even after that phase of play has ended. Players can be sent off following review and even at halftime if guilty of violent conduct, biting, spitting or making offensive gestures.
IFAB's technical director David Elleray told The Times that the rules changes are a precaution. "We do not anticipate this happening very often," he said. "However, if there is something away from the action that has been missed and it later comes to the attention of the VAR or the assistant VAR, then they can inform the referee and he can send the player off, even if it is later in the match. This would only be for serious red-card offences."

Source: ESPN