An improper certificate validation vulnerability in Fortinet FortiOS 7.0.0 - 7.0.13, 7.2.0 - 7.2.6, 7.4.0 - 7.4.1 and 6.4 all versions allows a remote and unauthenticated attacker to perform a Man-in-the-Middle attack on the FortiLink communication channel between the FortiOS device and FortiSwitch.