Your cat will be influenced by cannabis even in low doses so it is best to avoid this. Many cats are curious of what you do and that extents to when you consume cannabis.
I do not know how dangerous cannabis smoke is to cats, but I am not willing to find out. So may I suggest you keep your cat away from inhaling the vapour just to be safe.
While the effects of cannabis on humans are well know, on cats way less.
So the smoke is not the big issue, but if your cat starts eating the oil you use, that might kill it.
Luckily, marijuana intoxication is seldom fatal.
tldr: drugs have different effects on different species. What might be safe(ish) for humans can be lethal for pets. With many substances having unknown effects on pets.