Unpatched FortiGate Security Flaw Allows Attackers to Bypass 2FA Controls
## FortiGate Authentication Bypass Vulnerability
FortiGate Authentication Bypass Vulnerability
An authentication bypass vulnerability in FortiGate devices allows unauthorized access by manipulating the case sensitivity of usernames. This vulnerability, identified as CVE-2020-12812, affects systems with specific LDAP integration configurations. It remains a threat to unpatched systems.
The issue arises due to FortiGate's default case-sensitive username handling, which conflicts with LDAP directories that treat usernames as case-insensitive. Attackers can exploit this by altering the capitalization of legitimate usernames during login attempts, bypassing local 2FA-enabled accounts and triggering a fallback to less-secure LDAP group authentication.
Local FortiGate user entries with 2FA enabled linked to LDAP accounts LDAP group membership for those users Firewall policies using LDAP groups for authentication
An attacker can log in using altered capitalization (e.g., "Jsmith" instead of "jsmith"), bypassing local user policies and causing FortiGate to authenticate directly against the LDAP server using only username and password, ignoring 2FA requirements and disabled account statuses.
An authentication bypass vulnerability in FortiGate devices allows unauthorized access by manipulating the case sensitivity of usernames.
This vulnerability poses significant risks, including unauthorized access to administrative interfaces or corporate networks without 2FA tokens. Organizations affected should reset all credentials, including LDAP/AD binding accounts, as the attack leaves minimal forensic evidence.
Fortinet addressed this vulnerability in July 2020. Administrators should implement the set username-case-sensitivity disable command for FortiOS versions 6.0.10, 6.2.4, and 6.4.1. For later releases (6.0.13+, 6.2.10+, 6.4.7+, 7.0.1+), use set username-sensitivity disable to ensure uniform treatment of all username case variations and prevent authentication fallback.
Additional security measures include removing unnecessary secondary LDAP groups from authentication policies and auditing firewall configurations to eliminate redundant LDAP group references. This ensures strict local user matching and, where LDAP groups are non-essential, their complete removal blocks the authentication bypass pathway entirely.
Based on reporting by GBHackers.