FortiosOperating system · Fortinet
CVE-2021-24012
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedAn improper following of a certificate's chain of trust vulnerability in FortiGate versions 6.4.0 to 6.4.4 may allow an LDAP user to connect to SSLVPN with any certificate that is signed by a trusted Certificate Authority.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceFortiGate versions 6.4.0 to 6.4.4 contain an improper certificate chain of trust validation flaw in the SSLVPN authentication for LDAP users. The device fails to properly validate the full certificate chain, instead accepting any certificate signed by a trusted Certificate Authority without verifying the certificate belongs to the authenticating user. This allows authentication bypass using certificates from trusted CAs that were not issued to the legitimate user.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
FortiosOperating system
>= 6.4.0, < 6.4.5CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check FortiOS versionRun 'get system status' or 'fwut -v' via CLI to retrieve the installed FortiOS versionAffected if Version is 6.4.0, 6.4.1, 6.4.2, 6.4.3, or 6.4.4 (versions 6.4.0 through 6.4.4 are affected)
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Confirm SSLVPN is enabledRun 'get vpn ssl settings' via CLI to check if SSLVPN is configured and activeAffected if SSLVPN is enabled and operational
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Verify LDAP authentication is configured for SSLVPNRun 'get vpn ssl web portal' and 'get user ldap' via CLI to identify LDAP servers linked to SSLVPNAffected if LDAP servers are configured as authentication sources for SSLVPN
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Inspect certificate verification settings for LDAPRun 'get user ldap' and check for certificate-related parameters; review 'config user ldap' in configuration mode to see if 'cert-verify' or 'ca-cert' options are properly configuredAffected if Certificate verification is not enforced or is misconfigured, allowing any trusted CA certificate to authenticate
You are affected if your FortiGate runs FortiOS 6.4.0-6.4.4, SSLVPN is active, LDAP authentication is configured for SSLVPN, and certificate chain validation is not properly enforced.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data6.4.5
Upgrade FortiGate to version 6.4.5 or later (or 7.0+) to patch the certificate validation vulnerability. As a temporary measure, consider implementing additional authentication factors or restricting CA trust to only necessary issuers.
Fix this in Fortios
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,120.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-24012 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-24012 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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