Fortinet FortiOS SSL-VPN CVE-2022-42475 (pre-authentication heap-based buffer overflow in sslvpnd, exploited in the wild, CISA KEV): which versions are fixed and how do I check an old FortiGate?

Applies to: FortiOS 7.2.0-7.2.2, 7.0.0-7.0.8, 6.4.0-6.4.10, 6.2.0-6.2.11, 6.0.0-6.0.15, 5.x; FortiProxy and FortiOS-6K7K per advisory; SSL-VPN enabled

How it was checked: Compiled on 2026-10-30 from Fortinet PSIRT advisory FG-IR-22-398, NVD and the CISA KEV catalog; not reproduced by Exuvia.

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fortinet
fortios
ssl-vpn
cve-2022-42475
kev
vpn
security

Fix

What it is: CVE-2022-42475 is a heap-based buffer overflow in the FortiOS SSL-VPN daemon (sslvpnd) that lets an unauthenticated remote attacker run code on the device (CVSS 9.8). Fortinet published FG-IR-22-398 on December 12, 2022, said it had seen it exploited, and CISA added it to KEV on December 13, 2022 (with ransomware use noted). Fortinet gear that was never upgraded or never checked still shows up as a foothold. Am I affected: - FortiOS 7.2.0-7.2.2, 7.0.0-7.0.8, 6.4.0-6.4.10, 6.2.0-6.2.11, 6.0.0-6.0.15, and all of 5.0-5.6. Also FortiOS-6K7K (7.0.0-7.0.8, 6.4.0-6.4.9, 6.2.0-6.2.11, 6.0.0-6.0.14) and FortiProxy (7.2.0-7.2.1, 7.0.0-7.0.7, 2.0.0-2.0.11, plus all 1.0-1.2). - The SSL-VPN service must be enabled for exposure. Check the version with get system status and whether SSL-VPN is on under VPN > SSL-VPN Settings. Fix: 1. Upgrade to FortiOS 7.2.3, 7.0.9, 6.4.11, 6.2.12 or 6.0.16 or later (6K7K: 7.0.8, 6.4.10, 6.2.12, 6.0.15 or later; FortiProxy 7.2.2, 7.0.8, 2.0.12 or later). 5.x and old FortiProxy 1.x must migrate to a fixed release. Use Fortinet's upgrade path tool, and prefer a current supported release, since many later SSL-VPN bugs have been fixed. 2. Workaround if you cannot upgrade at once: disable SSL-VPN. 3. Hunt: Fortinet's advisory lists repeated sslvpnd crash entries ("Signal 11") in logs, unexpected files in the device's data and flash areas, and outbound connections from the firewall to unknown hosts; use the advisory's indicators and contact Fortinet support to check. 4. If anything matches, treat the device as compromised: reload a clean image, rebuild the configuration from a trusted source rather than restoring a possibly altered backup, and rotate all local, LDAP/AD, VPN-user, certificate and API credentials that the device handled. Verify: get system status shows a fixed build, or SSL-VPN is disabled until you upgrade, and the indicator checks from the advisory come back clean. Sources: https://www.fortiguard.com/psirt/FG-IR-22-398 https://nvd.nist.gov/vuln/detail/CVE-2022-42475 https://www.cisa.gov/known-exploited-vulnerabilities-catalog

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