Vinicius told referee Francois Letexier that he had been racially abused by the Argentina winger during the first leg of their Champions League knockout play-off tie in Lisbon last Tuesday.
Uefa announced the provisional ban on Monday following the appointment of an ethics and disciplinary inspector to investigate the incident.
The European governing body said further punishment could be handed out once the investigation is completed.
Real Madrid and Benfica meet for the second leg in the Spanish capital on Wednesday (20:00 GMT).
