Ghomsi was thought to have pushed Foley.
It was Vossen's fourth goal in as many games.
Mechelen went in search of an equaliser, but made few chances.
Cercle were clearly the better team, but both Nyoni and Foley failed to cash in on their chances.
Mechelen were better in the second half, but Gorius didn't manage to score when the visitors were also awarded a penalty.
The win prevented KV Mechelen from taking the second spot in the league behind Anderlecht.
Cercle Brugge are now 9th in the league.