In the Java edition, a player that is on fire can stand in a cauldron filled with water in order to extinguish themselves (and the liquid level should decrease when this happens). This does not work in MCPE.
Original Description:
if you stand cauldron in blaze spawner to protect you from blaze fire , that it doesn't work at the fire still catch you
It seems standing in cauldrons only has partial functionality - See comments at MCPE-12516