Two processes sharing memory under different privileged users

Question

I have two processes sharing memory (via Boost Interprocess). Each process is run under a different user. The first process is run from one of our privileged users.

The second process is ran via a user setup because we are using third party software (which we modify and recompile), therefore they need access to our system to update the headers etc.

I'm worried how will the two processes share memory, when its different users creating the shared memory.

Is there a way both users can access this shared memory, without the vendor user being granted the same system-wide privileges as our main user?

This is on CentOS 7.4