Versions Affected : All verisons prior to FreeNAS 11.3-U4.1
When handling a 32-bit sendmsg(2) call, the compat32 subsystem copies the control message to be transmitted (if any) into kernel memory, and adjusts alignment of control message headers.
The code which performs this work contained a time-of-check to time-of-use (TOCTOU) vulnerability which allows a malicious userspace program to modify control message headers after they were validated by the kernel. The TOCTOU bug can be exploited by an unprivileged malicious userspace program to trigger privilege escalation.
No workaround is available.
- Upgrade to FreeNAS 11.3-U5 or later.