Fortinet has begun releasing security updates to address a critical vulnerability in FortiOS that is being actively exploited in the wild.

Vulnerability Overview

The vulnerability, assigned CVE-2026-24858 with a CVSS score of 9.4, has been described as an authentication bypass related to FortiOS single sign-on (SSO).

Successful exploitation could allow an unauthenticated attacker to bypass authentication mechanisms and gain unauthorized access to protected resources.

Impact

This vulnerability affects organizations using FortiOS SSO for authentication. Given the critical severity rating and active exploitation status, the risk of compromise is significant for unpatched systems.

Remediation

Fortinet has released patches addressing this vulnerability. Organizations should:

  1. Update immediately to the latest FortiOS version
  2. Review authentication logs for suspicious activity
  3. Implement network segmentation to limit exposure
  4. Enable multi-factor authentication where possible as a defense-in-depth measure

Indicators of Compromise

Organizations should monitor for:

  • Unusual authentication patterns
  • Access from unexpected geographic locations
  • Authentication events without corresponding user activity

Contact Fortinet support or consult the official security advisory for detailed IoC information.