CVE-2020-12812: Fortinet FortiOS SSL VPN Improper Authentication Vulnerability

Fortinet FortiOS SSL VPN contains an authentication flaw where changing the case of the username enables a user to bypass the second-factor authentication prompt, specifically the FortiToken requirement. This improper authentication vulnerability (CWE-178, CWE-287) allows unauthorized access despite multi-factor authentication being configured. The vulnerability has been actively exploited in the wild and is associated with ransomware campaigns.

An attacker can successfully authenticate to the FortiOS SSL VPN without completing the second-factor authentication step, potentially gaining unauthorized access to the VPN. This undermines the security provided by multi-factor authentication and increases the risk of unauthorized network access and subsequent malicious activity, including ransomware deployment.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, organizations should consider additional compensating controls such as monitoring for unusual login patterns, enforcing strict username case policies, or temporarily disabling SSL VPN access if feasible.