It was found that ssh-agent could load PKCS#11 modules from arbitrary paths. An attacker having control of the forwarded agent-socket on the server, and the ability to write to the filesystem of the client host, could use this flaw to execute arbitrary code with the privileges of the user running ssh-agent.
It was found that ssh-agent could load PKCS#11 modules from paths outside of a trusted whitelist. An attacker able to load a crafted PKCS#11 module across a forwarded agent channel could potentially use this flaw to execute arbitrary code on the system running the ssh-agent. Note that the attacker must have control of the forwarded agent-socket and the ability to write to the filesystem of the host running ssh-agent.
This issue was fixed by only allowing the loading of module from a trusted (and configurable) whitelist.
Created openssh tracking bugs for this issue:
Affects: fedora-all [bug 1406296]
If we will want to fix it, we need to change the whitelist to something reasonable, because all of our PKCS#11 libraries are on x68_64 under /usr/lib64/
See the upstream discussion:
In order to exploit this flaw, the attacker needs to have control of the forwarded agent-socket and the ability to write to the filesystem of the host running ssh-agent. Because of this restriction for successful exploitation, this issue has been rated as having Moderate security impact. A future update may address this flaw.
This issue has been addressed in the following products:
Red Hat Enterprise Linux 7
Via RHSA-2017:2029 https://access.redhat.com/errata/RHSA-2017:2029