It’s not possible to update just NodeJS at this time.
A new version of firmware is coming that addresses the older version. We hope to have it released by the end of the year.
The version of Node-RED is tied to the version of nodejs, so we are running the most recent version of Node-RED that the version of nodejs will allow.
That is the most recent version of firmware.
You can find this here: Opto22 - groov RIO Module Firmware
Also I usually post to the forums as soon as a new version of firmware becomes available for both EPIC and RIO.