The version of OpenVPN that we use will always be a couple of versions behind the newest version OpenVPN offers. This is by design, as it gives us more flexibility in testing the functionality & security features of the version we include in Untangle.
It's not possible to upgrade the Untangle's built-in version of OpenVPN, as we design our software to work with the specific version we have installed. However, we do update all apps — including OpenVPN — through updates to our software. Our update change logs can be found here: