Three security vulnerabilities in the Fortinet SSL VPN are being used to gain a foothold within networks before moving laterally and carrying out reconnaissance. The FBI and the Cybersecurity and Infrastructure Security Agency are warning that advanced persistent threat (APT) nation-state actors are actively exploiting known security vulnerabilities in the Fortinet FortiOS cybersecurity operating system, affecting the company’s SSL VPN products. Cyber attackers are scanning devices on ports 4443, 8443 and 10443, looking for unpatched Fortinet security implementations.
APTs are exploiting CVE-2018-13379. In 2019, CVE-2018-13379 was extensively exploited in attacks in which unpatched VPN servers were targeted by Nation-State attackers. It was also exploited in the FireEye hack in December 2020. In addition, APTs are also exploiting two other vulnerabilities:
CVE-2019-5591 : A Default Configuration vulnerability in FortiOS may allow an unauthenticated attacker on the same subnet to intercept sensitive information by impersonating the LDAP server.
CVE-2020-12812: An improper authentication vulnerability in SSL VPN in FortiOS 6.4.0, 6.2.0 to 6.2.3, 6.0.9 and below may result in a user being able to log in successfully without being prompted for the second factor of authentication (FortiToken) if they changed the case of their username.
These vulnerabilities are being exploited to gain access to multiple government, commercial, and technology services networks. These three vulnerabilities targeting the Fortinet VPN allow an attacker to obtain valid credentials, bypass multifactor authentication (MFA), and man-in-the-middle (MITM) authentication traffic to intercept credentials.
SSL VPN vulnerabilities have been an attractive target for APT groups and cybercriminals alike. With the shift to remote work and the increased demand for SSL VPNs like Fortinet and others, the attack surface and available targets have expanded. Organizations should prioritize patching their Fortinet devices immediately if they haven’t done so already.
Organizations should take the following steps to mitigate this exploitation: