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Vulnerability record · CVE-2021-24020 · published 9 July 2021

CVE-2021-24020: Fortinet fortimail improper verification of cryptographic signature vulnerability

Fortinet · Fortimail

A missing cryptographic step in the implementation of the hash digest algorithm in FortiMail 6.4.0 through 6.4.4, and 6.2.0 through 6.2.7 may allow an unauthenticated attacker to tamper with signed URLs by appending further data which allows bypass of signature verification.

9.8 CVSS 3.1 Critical EPSS 0.62% · top 52.6% CWE-347 · Improper verification of cryptographic signature
9.8CVSS 3.1 base score, v2 7.5
0.62%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

Description

A missing cryptographic step in the implementation of the hash digest algorithm in FortiMail 6.4.0 through 6.4.4, and 6.2.0 through 6.2.7 may allow an unauthenticated attacker to tamper with signed URLs by appending further data which allows bypass of signature verification.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://fortiguard.com/advisory/FG-IR-21-027 Vendor Advisory
https://fortiguard.com/advisory/FG-IR-21-027 Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-24020), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.