CVE-2020-12820: Fortinet FortiOS

High severity, CVSS 8.8. EPSS: 0.9% chance of exploitation in the next 30 days.

Under non-default configuration, a stack-based buffer overflow in FortiOS version 6.0.10 and below, version 5.6.12 and below may allow a remote attacker authenticated to the SSL VPN to crash the FortiClient NAC daemon (fcnacd) and potentially execute arbitrary code via requesting a large FortiClient file name. We are not aware of proof of concept code successfully achieving the latter.

Affected products

• Fortinet FortiOS: before 5.6.13 (fixed in 5.6.13); from 6.0.0, before 6.0.11 (fixed in 6.0.11)

Published 2024-12-19. Last modified 2026-06-17.