CVE-2021-24012Network attack vector

SSL VPN access via incomplete certificate validation

Published Jun 2, 2021 · Updated Oct 25, 2024

Improper certificate validation in Fortinet FortiOS 6.4.0 through 6.4.4 allows remote authenticated users to use SSL VPN via unrelated certificates. During LDAP-integrated certificate authentication, FortiOS accepts a certificate that chains to a trusted CA without ensuring that its identity belongs to the LDAP user. Exploitation requires valid LDAP credentials, SSL VPN configured for certificate authentication, and a certificate issued by a trusted CA; the result is VPN access that the certificate policy should deny.

CVSS severity7.3
High
EPSS probability0.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in Fortinet FortiOS 6.4.0 through 6.4.4 allows remote authenticated users to use SSL VPN via unrelated certificates. During LDAP-integrated certificate authentication, FortiOS accepts a certificate that chains to a trusted CA without ensuring that its identity belongs to the LDAP user. Exploitation requires valid LDAP credentials, SSL VPN configured for certificate authentication, and a certificate issued by a trusted CA; the result is VPN access that the certificate policy should deny.

The record

CVE
CVE-2021-24012
Published
Jun 2, 2021
Updated
Oct 25, 2024
Vendor
Fortinet
Product
FortiOS
Classifications
CWE-295, T1133
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 2, 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=FortiOS 6.4.0 to 6.4.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Fortinet · FortiOSversion=FortiOS 6.4.0 to 6.4.4

Published CVSS scores

6.5FortinetCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:L
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
7.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

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

CWE-295Improper Certificate Validation
T1133External Remote Services

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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