It would appear that centos 7.5 with tftp server 5.2.22 (or later or post Feb 2018) has the RFC7440 patch applied. https://rpmfind.net/linux/RPM/centos/7.7.1908/x86_64/Packages/tftp-server-5.2-22.el7.x86_64.html
My fog server that runs on centos 7 appears to have the required version of in.tfpd
tftp-server-5.2-22.el7.x86_64 : The server for the Trivial File Transfer Protocol (TFTP) Repo : base Matched from: Filename : /usr/sbin/in.tftpd