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Deploying Fortinet VPN with default settings can leave your organization open to attack

Deploying Fortinet VPN with default settings can leave your organization open to attack

2020-09-30 20:42:14
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Over 200,000 businesses that have deployed Fortinet VPN with its default configuration could be vulnerable to man-in-the-middle (MitM) attacks according to new research from the network security company SAM Seamless Network.

With more employees working from home than ever before, organizations around the world have turned to VPN services to provide their workers with an easy way to connect to their corporate networks. However, cybercriminals are well aware of this and have begun to look for weakness they can exploit in organization’s VPN configurations.

After closely examining Fortinet’s Fortigate VPN solution, security researchers at SAM seamless network realized that under the default configuration the company’s SSL VPN is not as protected as it should be and is vulnerable to MitM attacks. This is because the Fortigate SSL-VPN client only verifies that the SSL certificate was issued by Fortigate or another trusted certificate authority (CA).

An attacker could take advantage of this to launch MitM attacks by presenting a certificate issued to a different Fortigate router without raising any flags. In just a matter of minutes, the researchers conducted a search and found over 200k vulnerable businesses that were still using Fortinet VPN’s default configuration despite the fact that the company explicitly warns users about using a default built-in certificate.

Default certificate

All Fortigate routers ship with a default SSL certificate that is signed by Fortinet but this certificate can be spoofed by a third-party or even an attacker as long as it’s valid and issued by Fortinet or a trusted CA.

All of the company’s default SSL certificates use a router’s serial number as the server name for the certificate. While the company could use the router’s serial number to check if the server names match, the client appears to not verify the server name at all according to SAM Seamless Network’s research. The researchers even designed a MitM proof of concept (PoC) to show how an attacker can easily re-route the traffic to their server, display their own certificate, and then decrypt an organization’s VPN traffic.

In Fortinet’s defense, the company’s client displays the following warning when a customer uses the default certificate: “You are using a default built-in certificate, which will not be able to verify your server’s domain name (your users will see a warning). It is recommended to purchase a certificate for your domain and upload it for use.”

At the moment, Fortinet has no plans to address this issue as users can manually replace the default certificate on their own to protect their networks from MitM attacks. The company offered further details on the matter in a statement to The Hacker News, which reads:

“The security of our customers is our first priority. This is not a vulnerability. Fortinet VPN appliances are designed to work out-of-the-box for customers so that organizations are enabled to set up their appliance customized to their own unique deployment. Each VPN appliance and the set up process provides multiple clear warnings in the GUI with documentation offering guidance on certificate authentication and sample certificate authentication and configuration examples. Fortinet strongly recommends adhering to its provided installation documentation and process, paying close attention to warnings throughout that process to avoid exposing the organization to risk.”

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Via The Hacker News


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