Shared memory is an efficient means of passing data between programs. Because two or more processes can use the same memory space, it has been discovered that, since shared memory is, by default, mounted as read/write, the /run/shm space can be easily exploited.
That translates to a weakened state of security.
If you’re unaware, shared memory can be used in an attack against a running service. Because of this, you’ll want to secure that portion of system memory.