CVE-2024-55591 : Fortinet FortiOS Authentication Bypass Vulnerability

CVE-2024-55591 is a critical authentication bypass vulnerability affecting Fortinet’s FortiOS and FortiProxy systems.

This flaw, rated with a CVSS score of 9.8, allows unauthenticated attackers to gain super-admin privileges by exploiting improper handling of session tokens in the Node.js WebSocket module.

The vulnerability has been actively exploited in the wild since November 2024, posing significant risks to enterprise networks.

The vulnerability stems from a chain of issues:

• Attackers can initiate WebSocket connections from pre-authenticated HTTP requests.
• A parameter (local_access_token) bypasses session checks.
• Exploiting race conditions in the WebSocket communication with the CLI process allows attackers to authenticate as super-admins.

Successful exploitation enables attackers to:

• Gain unauthorized access.
• Execute arbitrary commands.
• Escalate privileges.
• Compromise internal networks by creating rogue accounts, modifying configurations, and tunneling through SSL VPNs.

The vulnerability impacts:

• FortiOS: Versions 7.0.0 through 7.0.16.
• FortiProxy: Versions 7.0.0 through 7.0.19 and 7.2.0 through 7.2.12.

Tools like the CVE-2024-55591-check.py script can identify vulnerable systems by attempting WebSocket connections to management interfaces and analyzing responses.

Indicators of compromise (IoCs) include unauthorized admin account creation, unexpected policy changes, and rogue SSL VPN users.

Fortinet recommends:

1. Patching: Upgrade to FortiOS 7.0.17 or higher and FortiProxy 7.2.13 or higher.
2. Restricting Access: Disable HTTP/HTTPS administrative interfaces or limit access to trusted IPs using local-in policies.
3. Monitoring Logs: Look for signs of unauthorized logins, rogue accounts, or abnormal configuration changes.

CVE-2024-55591 highlights the importance of securing administrative interfaces and promptly applying patches to mitigate risks.

Organizations should prioritize updating affected systems and implementing strict access controls to prevent exploitation of this critical vulnerability.