CVE-2021-26091Network attack vector

Credential resets via predictable authentication tokens

Published Mar 24, 2025 · Updated Mar 31, 2025

Weak PRNG use in Fortinet FortiMail 6.2.0 through 6.2.9 and 6.4.0 through 6.4.4 allows remote attackers to reset credentials. The Identity Based Encryption authenticator generates password and token material with a noncryptographic PRNG, making portions of user authentication tokens inferable. No authentication is required, and successful inference enables credential resets for affected users.

CVSS severity7.5
High
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Weak PRNG use in Fortinet FortiMail 6.2.0 through 6.2.9 and 6.4.0 through 6.4.4 allows remote attackers to reset credentials. The Identity Based Encryption authenticator generates password and token material with a noncryptographic PRNG, making portions of user authentication tokens inferable. No authentication is required, and successful inference enables credential resets for affected users.

The record

CVE
CVE-2021-26091
Published
Mar 24, 2025
Updated
Mar 31, 2025
Vendor
Fortinet
Product
FortiMail
Classifications
CWE-338
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 24, 2025CVE publishedPublication date reported by the CVE source.
  2. Mar 31, 2025Record 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=6.2.0 <6.2.*
  2. Affected versionversion=6.2.0 <=6.2.9
  3. Affected versionversion=6.4.0 <=6.4.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Fortinet · FortiMailversion=6.2.0 <6.2.*; version=6.2.0 <=6.2.9; version=6.4.0 <=6.4.4

Published CVSS scores

7.5FortinetCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
6.9FortinetCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:U/RC:C

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-338Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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