CVE-2021-42756: Fortinet FortiWeb

Critical severity, CVSS 9.8. EPSS: 35% chance of exploitation in the next 30 days.

Multiple stack-based buffer overflow vulnerabilities [CWE-121] in the proxy daemon of FortiWeb 5.x all versions, 6.0.7 and below, 6.1.2 and below, 6.2.6 and below, 6.3.16 and below, 6.4 all versions may allow an unauthenticated remote attacker to achieve arbitrary code execution via specifically crafted HTTP requests.

Affected products

• Fortinet FortiWeb: from 5.6.0, before 6.0.8 (fixed in 6.0.8); from 6.1.0, before 6.1.3 (fixed in 6.1.3); from 6.2.0, before 6.2.7 (fixed in 6.2.7); from 6.3.0, before 6.3.17 (fixed in 6.3.17); from 6.4.0, up to and including 6.4.2

Published 2023-02-16. Last modified 2026-06-17.