The base operating system version for TrueNAS 11.0-U4 is FreeBSD 11-STABLE, bringing in a number of bug fixes, performance improvements, and new drivers. FreeBSD ports have been updated to follow the FreeBSD 2016Q4 branch.

TrueNAS 11.0-U4 includes the following fixes from FreeNAS:

11.0-RC: https://bugs.freenas.org/projects/freenas/issues?query_id=378

11.0-RC2: https://bugs.freenas.org/projects/freenas/issues?query_id=379

11.0-RC3: https://bugs.freenas.org/projects/freenas/issues?query_id=411

11.0-RC4: https://bugs.freenas.org/projects/freenas/issues?query_id=393

11.0: https://bugs.freenas.org/projects/freenas/issues?query_id=325

11.0-U1: https://bugs.freenas.org/projects/freenas/issues?query_id=404

11.0-U2: https://bugs.freenas.org/projects/freenas/issues?query_id=418 

11.0-U3: https://bugs.freenas.org/projects/freenas/issues?query_id=419 

11.0-U4: https://bugs.freenas.org/projects/freenas/issues?query_id=430 

In addition, these fixes are specific to TrueNAS 11.0-U4:

Patch base operating system to address FreeBSD SA 17:06.openssh:
https://www.freebsd.org/security/advisories/FreeBSD-SA-17:06.openssh.asc.

Update Samba version to 4.6.8 to address current CVEs:
https://www.samba.org/samba/history/samba-4.6.8.html.

Prevent the configuration of the failover lagg type on HA systems. This lagg
type fails over too slowly for High Availability environments.

Improvements to ensure that a system automatically rejoins the Active Directory
network after an HA failover.