FreeBSD Security Advisory – The ssh-agent(1) agent supports loading a PKCS#11 module from outside a trusted whitelist. An attacker can request loading of a PKCS#11 module across forwarded agent-socket. When privilege separation is disabled, forwarded Unix domain sockets would be created by sshd(8) with the privileges of ‘root’ instead of the authenticated user. A remote attacker who have control of a forwarded agent-socket on a remote system and have the ability to write files on the system running ssh-agent(1) agent can run arbitrary code under the same user credential. Because the attacker must already have some control on both systems, it is relatively hard to exploit this vulnerability in a practical attack. When privilege separation is disabled (on FreeBSD, privilege separation is enabled by default and has to be explicitly disabled), an authenticated attacker can potentially gain root privileges on systems running OpenSSH server.