FreeBSD: VID-5b1463dd-dab3-11e7-b5af-a4badb2f4699 (CVE-2017-1087): FreeBSD -- POSIX shm allows jails to access global namespace

Problem Description: Named paths are globally scoped, meaning a process located in one jail can read and modify the content of POSIX shared memory objects created by a process in another jail or the host system. Impact: A malicious user that has access to a jailed system is able to abuse shared memory by injecting malicious content in the shared memory region. This memory region might be executed by applications trusting the shared memory, like Squid. This issue could lead to a Denial of Service or local privilege escalation.