REX640 Protection Relay Firmware Update Release 1.2.1

This document announces firmware update release 1.2.1 for ABB REX640 protection relays and LHMIs, applicable to units delivered before February 3, 2022, with Product Connectivity Level 3 (PCL3) and firmware version 1.2. The update includes cyber security fixes (notably CVE-2021-22283 for MMS file transfer vulnerability), supervision improvements for PKI certificate renewal, User Account Management enhancements, and HMI/WHMI stability and language fallback improvements.