No exploitation reportedFix available

CVE-2021-36166

Q: Is CVE-2021-36166 actively exploited?

Active exploitation of CVE-2021-36166 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-2021-36166?

CVE-2021-36166 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.

Published2022-03-01
Fixed in6.4.6 · 6.2.8 · 6.0.12
WeaknessCWE-330

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

An improper authentication vulnerability in FortiMail before 7.0.1 may allow a remote attacker to efficiently guess one administrative account's authentication token by means of the observation of certain system's properties.

Timeline

dates in UTC

2022-03-0118:15CVE 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-2021-36166?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-36166?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Fortinet fortimail

Branch	Affected	Fixed in	Source
6.4	≥ 6.4.0, < 6.4.6	6.4.6	NVD
6.2	≥ 6.2.0, < 6.2.8	6.2.8	NVD
6.0	≥ 6.0.0, < 6.0.12	6.0.12	NVD
5.4	≤ 5.4.12	no fix published	NVD
7.0	= 7.0.0	no fix published	NVD

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

Fix

Update Fortinet fortimail to 6.4.6 · 6.2.8 · 6.0.12

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 3.19.8read 2026-10-23
NVDCVSS 3.19.8read 2026-10-23
NVDCVSS 2.07.5read 2026-10-23
NVDweakness (CWE)CWE-330read 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: 2022-03-01
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-36166?

Is CVE-2021-36166 actively exploited?

Active exploitation of CVE-2021-36166 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-2021-36166?

CVE-2021-36166 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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