CVE-2021-36166

CRITICALNVD 9.89.8—

9.8

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.

CVSS v3: 9.8
EG Score: 9.8(medium)
EPSS: 66.4%
KEV: Not listed

Published

March 1, 2022

Last Modified

November 21, 2024

References (2)

psirt@fortinethttps://fortiguard.com/psirt/FG-IR-21-028
af854a3a-2127-422b-91ae-364da2661108https://fortiguard.com/psirt/FG-IR-21-028

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 20× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-06-02 20:11 UTCepss_batch
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2026-06-01 13:50 UTCepss_batch
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2026-05-31 22:29 UTCepss_batch
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2026-05-29 13:42 UTCepss_batch
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2026-05-28 13:43 UTCepss_batch
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2026-05-27 13:39 UTCepss_batch
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2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
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2026-05-26 07:17 UTCepss_batch
2026-05-26 02:19 UTCEG score recompute

Frequently asked(5)

What is CVE-2021-36166?

CVE-2021-36166 is a critical vulnerability published on March 1, 2022. 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.

When was CVE-2021-36166 disclosed?

CVE-2021-36166 was first published in the National Vulnerability Database on March 1, 2022, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-36166 actively exploited?

CVE-2021-36166 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 66.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-36166?

CVE-2021-36166 has a CVSS v3 base score of 9.8 (NVD).

How do I remediate CVE-2021-36166?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-36166, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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CVE-2021-36166

📅 Published

🔄 Last Modified

🔗 References (2)

Weakness Classification(2)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-36166?

🔗 Related CVEs(same CWE)

Same CWE

Published

Last Modified

References (2)

Frequently asked(5)

Related CVEs(same CWE)