Is it known how easy it is to trigger the memory leak?

I came across this just the other day..

https://github.com/MatAtBread/fast-async

As a not-elligible-for-LTS version, it's probably fine - you're not going to be using Node 7 in production anyway, as it's only ever a cutting-edge release, unless you don't care about stability in which case memleaks are part and parcel.