I am a Bangladeshi national traveling from London to Toronto, Canada through CDG Paris, France by Air France. My transit time at CDG is 4h55m. Do I need an airport transit visa for this travel?
All the rules are explained in Do I need a visa to transit in the Schengen area?
Citizens of Bangladesh do require an airport transit visa (ATV) in France and elsewhere in the Schengen area but since you are traveling from the UK to Canada, it's safe to assume that you have either a residence permit or a visa for each of these countries and any one of these documents would exempt you from the ATV requirement. If that's indeed the case, you don't need a visa for this connection.