ᐅ Leakage at the ventilation pipe on the roof

Hello everyone,

I recently noticed a water stain on the ceiling in my grandfather’s upper floor.

I went up to the unfinished attic to take a closer look.

The culprit is the ventilation pipe. The spot where it protrudes through the roof appears to be leaking.

I resealed the area on the roof with special silicone, but a little moisture is still getting in.

I also noticed that the roofing membrane around the pipe is only cut out and not fixed in place.

Do you think it would be enough to seal it with special tape designed for roofing membranes? In other words, preventing moisture from getting under the membrane – would that hold?

Is it not a big problem if a bit of moisture gets between the tiles and the roofing membrane around the pipe?

Pictures attached.

Thanks and best regards