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Fortinet vulnerability CVE-2026-22153 is an authentication bypass in FortiOS that can affect LDAP authentication for Agentless VPN or FSSO policy under a specific remote LDAP configuration. Singapore’s Cyber Security Agency (CSA) lists FortiOS 7.6.0 through 7.6.4 as affected and advises administrators to update immediately. The CSA advisory does not identify the first fixed release, so verify the target version and device upgrade path in Fortinet’s current PSIRT advisory before upgrading.
What CVE-2026-22153 does
The flaw can allow an unauthenticated attacker to bypass LDAP authentication used by Agentless VPN or FSSO policy. If the affected configuration is in place, an attacker could potentially access network resources without valid credentials.
This is not described as a bypass of every FortiOS authentication method or every LDAP setup. The CSA ties the impact to a specific configuration of the remote LDAP server and the stated Agentless VPN or FSSO policy context. Review whether those conditions apply to your deployment.
Which FortiOS versions are affected?
The CSA advisory names FortiOS versions 7.6.0 through 7.6.4 as affected by CVE-2026-22153. It does not establish whether other FortiOS branches are affected.
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The advisory was published on 16 February 2026 and was last updated on 1 October 2026. See the CSA advisory, “High Severity Vulnerabilities in Fortinet Products”, which links to Fortinet PSIRT reference FG-IR-25-1052.
What administrators should do
- Check the FortiOS version. Confirm whether each relevant device runs 7.6.0, 7.6.1, 7.6.2, 7.6.3, or 7.6.4.
- Check the configuration context. Determine whether LDAP authentication is used for Agentless VPN or FSSO policy and whether the remote LDAP configuration described by Fortinet applies.
- Consult Fortinet PSIRT advisory FG-IR-25-1052. Identify the fixed release for your branch and confirm the supported upgrade path for the specific device. Do not infer a fixed version from the CSA’s affected range.
- Update promptly. The CSA advises users and administrators of affected versions to update immediately. Follow the vendor’s version-specific upgrade guidance.
What is not confirmed by the CSA notice
The CSA advisory does not state the first fixed FortiOS release, nor does it establish the status of branches outside 7.6.0 through 7.6.4. Administrators should use Fortinet’s current PSIRT advisory to resolve those questions rather than treating the end of the affected range as the fix.
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