CVE-2021-26095Network attack vector

Privilege escalation via forgeable encrypted session cookies

Published Jul 20, 2021 · Updated Oct 25, 2024

Cryptographic flaws in Fortinet FortiMail 6.4.0 through 6.4.4 and 6.2.0 through 6.2.6 allow remote authenticated users to escalate privileges. The session manager uses a flawed encryption construction for session cookies, allowing an existing cookie's contents to be revealed, altered, or forged. Exploitation requires possession of a valid cookie; forged session data can grant higher privileges and compromise protected mail-system functions.

CVSS severity8.8
High
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cryptographic flaws in Fortinet FortiMail 6.4.0 through 6.4.4 and 6.2.0 through 6.2.6 allow remote authenticated users to escalate privileges. The session manager uses a flawed encryption construction for session cookies, allowing an existing cookie's contents to be revealed, altered, or forged. Exploitation requires possession of a valid cookie; forged session data can grant higher privileges and compromise protected mail-system functions.

The record

CVE
CVE-2021-26095
Published
Jul 20, 2021
Updated
Oct 25, 2024
Vendor
Fortinet
Product
FortiMail
Classifications
T1550.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 20, 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 6.4.0 through 6.4.4 and 6.2.0 through 6.2.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Fortinet · FortiMailversion=FortiMail 6.4.0 through 6.4.4 and 6.2.0 through 6.2.6

Published CVSS scores

6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.5Fortinet, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1550.004Web Session Cookie

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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