I've been lucky enough to fly into a couple of CBs unintentionally and not have anything too bad happen. Both times was during a commercial medical flight in a piston twin in Europe which was equipped only with the world's worst stormscope. Both times it was very bumpy and both times lost comms until we cleared it, one time was exceptionally rough and after telling ATC we had just inadvertently flew into one and were experiencing sever turbulence they gave us "speed, altitude and heading at your discretion".
The joys of flying from A to B in solid IMC without much means of determining what type of IMC you are actually in.