No exploitation reportedFix available

CVE-2021-42761

Q: Is CVE-2021-42761 actively exploited?

Active exploitation of CVE-2021-42761 has not been confirmed. Its EPSS score was 1.5% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-42761?

CVE-2021-42761 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

No exploitation reported by the sources we read.

Published2023-02-16
Fixed in7.0.0 · 6.3.17 · 6.2.7 · 6.1.3 · 6.0.8 · 5.9.2
WeaknessCWE-384

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC

2023-02-1619:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-42761?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-42761?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Fortinet fortiweb

Branch	Affected	Fixed in	Source
7.0	≥ 6.4.0, < 7.0.0	7.0.0	NVD
6.3	≥ 6.3.0, < 6.3.17	6.3.17	NVD
6.2	≥ 6.2.0, < 6.2.7	6.2.7	NVD
6.1	≥ 6.1.0, < 6.1.3	6.1.3	NVD
6.0	≥ 6.0.0, < 6.0.8	6.0.8	NVD
5.x	≥ 5.6.0, < 5.9.2	5.9.2	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Fortinet fortiweb to 7.0.0 · 6.3.17 · 6.2.7 · 6.1.3 · 6.0.8 · 5.9.2

Advisories and patches

fortiguard.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CISA-ADPSSVC decisionnone2024-10-23
OpenCVESSVC decisionnone—
CNACVSS 3.19read 2026-10-23
NVDCVSS 3.19.8read 2026-10-23
CNAweakness (CWE)CWE-384read 2026-10-23
NVDweakness (CWE)CWE-384read 2026-10-23
FIRST EPSSEPSS score1.5 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: 2023-02-16
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-42761?

Is CVE-2021-42761 actively exploited?

Active exploitation of CVE-2021-42761 has not been confirmed. Its EPSS score was 1.5% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-42761?

CVE-2021-42761 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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