Fortigate UTM appliances share the same self-signed Fortigate CA certificate. Companies that use these appliances for deep packet inspection will have most likely deployed the CA certificate to endpoint web browsers so certificate warnings will not be seen by an end-user. Since the associated private key has been compromised (published on the web), an attacker with a man-in-the-middle vantage point on the network will be able to simulate the behavior of the Fortigate appliance and eavesdrop on encrypted communications or spoof websites. Also, the attacker may digitally sign malicious software, spoofing the identity of the publisher.

Primarily at risk are users who have imported the compromised Fortigate CA certificate into their web browser or operating system. This risk applies equally within the company (connected to a network behind the Fortigate UTM appliance) as anywhere else. An attacker with a man-in-the-middle vantage point on the current network may be able to eavesdrop on encrypted communications. In addition, an attacker may falsify digital signatures such as Authenticode.

Install a new CA certificate

The vendor recommends the following steps be taken to address this vulnerability.

1. Admin creates/obtains a CA certificate for which only they have the private key.
2. Admin installs the CA certificate on FortiGate.
3. Admin uses "set caname xxx" to select that certificate for SSL deep inspection.