Ribery was sent off for a bad tackle on Lyon striker Lisandro Lopez in the 37th minute of Bayern's semi-final first leg against Olympique Lyon last week.
The red card meant he was automatically suspended for the second leg in France, which Bayern won 3-0 to reach the final with ease, and UEFA decided to add two further games to that punishment on Wednesday.
The final, to be held at Real Madrid's Santiago Bernabeu stadium on May 22, will be against Inter Milan or Barcelona.
Ribery's absence, if confirmed, would come as a significant blow to Bayern, who have reached the Champions League final for the first time since they last won the competition in 2001.
"I thought, watching from the bench, that he stood too long on the opponent's leg," Van Gaal said. "I do not think it was a red card because it was the inner foot and not a foul with full force."
NEWS:Bad week worsens for Ribery
