What’s Vulnerable › Vulnerabilities

CVE-2021-42761

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-02-16 · updated 2026-06-17
• Weakness: CWE-384

Description

A condition for session fixation vulnerability [CWE-384] in the session management of FortiWeb versions 6.4 all versions, 6.3.0 through 6.3.16, 6.2.0 through 6.2.6, 6.1.0 through 6.1.2, 6.0.0 through 6.0.7, 5.9.0 through 5.9.1 may allow a remote, unauthenticated attacker to infer the session identifier of other users and possibly usurp their session.

Affected products

• Fortinet FortiWeb: from 5.6.0 before 5.9.2; from 6.0.0 before 6.0.8; from 6.1.0 before 6.1.3; from 6.2.0 before 6.2.7; from 6.3.0 before 6.3.17; from 6.4.0 before 7.0.0 — fixed in 5.9.2, 6.0.8, 6.1.3, 6.2.7, 6.3.17, 7.0.0

How to fix

Upgrade to a fixed version: Fortinet FortiWeb 5.9.2, 6.0.8, 6.1.3, 6.2.7. Check the vendor advisory for mitigations.

References

• https://fortiguard.com/psirt/FG-IR-21-214
• https://fortiguard.com/psirt/FG-IR-21-214

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