Fortinet FortiNAC CVE-2022-39952 flaw exploited in the wild hours after the release of PoC exploit

Threat actors are actively exploiting the Fortinet FortiNAC vulnerability CVE-2022-39952 a few hours after the publication of the PoC exploit code.

This week, researchers at Horizon3 cybersecurity firm have released a proof-of-concept exploit for a critical-severity vulnerability, tracked as CVE-2022-39952, in Fortinet’s FortiNAC network access control solution.

Last week, Fortinet has released security updates to address two critical vulnerabilities in FortiNAC and FortiWeb solutions. The two vulnerabilities, tracked as CVE-2022-39952 and CVE-2021-42756, are respectively an external control of file name or path in Fortinet FortiNAC and a collection of stack-based buffer overflow issues in the proxy daemon of FortiWeb.

The CVE-2022-39952 flaw (CVSS score of 9.8) is an external control of file name or path in the keyUpload scriptlet of FortiNAC. The vulnerability was internally discovered and reported by Gwendal Guégniaud of Fortinet Product Security team.

“An external control of file name or path vulnerability [CWE-73]in FortiNAC webserver may allow an unauthenticated attacker to perform arbitrary write on the system.” reads the advisory.

The affected products are:

FortiNAC version 9.4.0
FortiNAC version 9.2.0 through 9.2.5
FortiNAC version 9.1.0 through 9.1.7
FortiNAC 8.8 all versions
FortiNAC 8.7 all versions
FortiNAC 8.6 all versions
FortiNAC 8.5 all versions
FortiNAC 8.3 all versions

The CVE-2022-39952 vulnerability is fixed in FortiNAC 9.4.1 and later, 9.2.6 and later, 9.1.8 and later, and 7.2.0 and later.

The PoC exploit code released by Horizon3 writes a cron job to /etc/cron.d/ that creates a reverse shell every minute.

Unfortunately, the threat actors started exploiting the Fortinet FortiNAC vulnerability CVE-2022-39952 the same day Horizon3 released the PoC exploit.

We are seeing @Fortinet FortiNAC CVE-2022-39952 exploitation attempts from multiple IPs in our honeypot sensors. A PoC was published earlier today. Make sure to upgrade your FortiNAC as specified in: https://t.co/edZEG2VOzL

— Shadowserver (@Shadowserver) February 21, 2023

The nonprofit cybersecurity organization Shadowserver reported that attackers started targeting its honeypots in an attempt to exploit the flaw.

Andrew Morris, the founder of CEO of GreyNoise Intelligence, also confirmed that his firm started observing broad exploitation of the FortiNAC CVE-2022-39952.

At the time of this writing, the attacks observed by GreyNoise originated from two IP addressed, respectively in Germany and the US.

Researchers German Fernandez from CronUp reported that threat actors have started with the mass deployment of Webshells (backdoors) on FortiNAC devices vulnerable to CVE-2022-39952.