Fortinet FortiOS SSL VPN Improper Authentication Vulnerability

What it is

Fortinet FortiOS SSL VPN contains an improper authentication vulnerability that may allow a user to login successfully without being prompted for the second factor of authentication (FortiToken) if they change the case in their username.

Known to be used in ransomware campaigns.Active threat actors have chained this vulnerability into ransomware operations — treat patching as a same-week priority, not a "next maintenance window" task. The coping action is the same one below; the urgency is higher.

Who's affected

Affects anyone whose internet connection goes through a Fortinet appliance — typically a FortiGate firewall or FortiClient VPN. The firewall sits between every device in the office and the internet; exploitation can mean an attacker gets inside the network perimeter without touching a workstation.

What to do

Apply updates per vendor instructions.

CISA action deadline: May 3, 2022. Federal agencies must complete the required action by this date. For private SMBs the deadline is advisory — but treat it as a strong recommendation, especially if you handle regulated data (HIPAA, GLBA, ABA model rules).

If you don't have someone in-house to verify the patch deployed across every endpoint — or you're not sure whether you're affected — that's exactly the kind of triage we do. Book a free 20-minute triage call.

Source

Pulled daily from the public cisagov/kev-data mirror (CC0). View the original entry on cisa.gov. CISA KEV is US-Government public-domain data; we add the SMB-vertical framing and the coping action above.

← All SMB-relevant KEV entries