Hi,
I'm not sure at this point how to reproduce it, I'll keep looking, but I wanted to bring this to your attention too because if it's true, this would be a nasty bug and it will hit you at one point. I opted to dig it out here, on the forums, rather than go to support with nothing concrete.

One necessary condition (not sufficient as I've discovered) is to have the Obj from which the hair is created scaled up uniformly at scene level - say to 2. After doing this, you'll notice an increased memory usage, compared to when rendering the same number of hairs but with the referenced object scaled at 1.
I noticed this happening on a “fresh” scene, one where little to grooming was done, or no or few process nodes applied. In a scene a bit more worked on, the leak is more likely to happen.

Also, I have not tried to scale up the Object at SOP lvl to see if this is still happening. You might wanna try that too on your side.

Thanks for posting. If it's really related to scale maybe it's something in the object merge or file SOPs that pull in the skin geometry.

I'll try to reproduce it. Please let us know if you happen to find the steps that reproduce this consistently.

Hey Kai,
Please check in with support.