Just as Fortinet is warning of threat actors maintaining persistent access to FortiOS and FortiProxy devices affected by known vulnerabilities, a threat actor is offering to sell an alleged zero-day exploit targeting FortiGate firewalls.
Over the weekend, cybersecurity firm ThreatMon warned on X of a post on a dark web forum, in which a threat actor claims that a zero-day in Fortinet’s FortiGate firewalls could be exploited remotely, without authentication, to execute arbitrary code.
According to the individual, the exploit would provide full control over a vulnerable device, enabling the extraction of FortiOS configuration files and the sensitive information they store, including credentials, admin account permissions, firewall policies, two-factor authentication status, and more.
SecurityWeek has emailed Fortinet for comment and will provide an update if necessary.
The threat actor’s post landed at the same time Fortinet released a fresh advisory on the exploitation of known vulnerabilities in its FortiOS and FortiProxy products.
According to Fortinet, at least three security defects for which patches have been released — CVE-2022-42475, CVE-2023-27997, and CVE-2024-21762 — have been exploited in global attacks to “implement read-only access to vulnerable FortiGate devices.”
By “creating a symbolic link connecting the user filesystem and the root filesystem in a folder used to serve language files for the SSL-VPN,” the attackers evade detection and ensured that, even after patches were deployed, they maintained access to the compromised devices.
Only configurations with SSL-VPN enabled have been affected, and Fortinet has deployed new mitigations, including an AV/IPS signature and modifications in recent software releases to detect and clean the symbolic link, and communication with the potentially impacted customers.
Fortinet and the US cybersecurity agency CISA urge administrators to update their firewalls to FortiOS versions 7.6.2, 7.4.7, 7.2.11, 7.0.17, or 6.4.16, which remove the malicious symbolic link.
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