CVE-2021-26100Network attack vector

Email plaintext recovery via missing cryptographic step

Published Jul 9, 2021 · Updated Oct 25, 2024

Cryptographic verification failure in Fortinet FortiMail before 7.0.0 allows man-in-the-middle attackers to recover email plaintext. The IBE service omits an unspecified cryptographic step, allowing intercepted ciphertext to be altered without tampering detection. Exploitation requires interception of encrypted messages and exposes their contents; no service interruption or configuration change is reported.

CVSS severity5.9
Medium
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cryptographic verification failure in Fortinet FortiMail before 7.0.0 allows man-in-the-middle attackers to recover email plaintext. The IBE service omits an unspecified cryptographic step, allowing intercepted ciphertext to be altered without tampering detection. Exploitation requires interception of encrypted messages and exposes their contents; no service interruption or configuration change is reported.

The record

CVE
CVE-2021-26100
Published
Jul 9, 2021
Updated
Oct 25, 2024
Vendor
Fortinet
Product
FortiMail
Classifications
CWE-347, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Oct 25, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=FortiMail before 7.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Fortinet · FortiMailversion=FortiMail before 7.0.0

Published CVSS scores

5.0NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:P/I:N/A:N
7.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
5.9Fortinet, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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