Yes, that is how rockets get to space, for example. Earth's atmo is ~21% Oxygen. So that is giving flames a boost. Careful not conflate "burn" with the presence of flames. In a vacuum, the flame could only exist briefly because there isnt the available Oxygen from the air. The reaction will (or might?) still happen, but without the oxygen to produce a flame.

BTW, this has been studied in microgravity aboard the ISS.