CVE-2023-50176: Fortinet FortiOS Auth Bypass Vulnerability

CVE-2023-50176 Overview

A session fixation in Fortinet FortiOS version 7.4.0 through 7.4.3 and 7.2.0 through 7.2.7 and 7.0.0 through 7.0.13 allows an attacker to execute unauthorized code or commands via a phishing SAML authentication link.

Critical Impact

Allows unauthorized code execution affecting multiple FortiOS versions.

Affected Products

• Fortinet FortiOS 7.4.0 to 7.4.3
• Fortinet FortiOS 7.2.0 to 7.2.7
• Fortinet FortiOS 7.0.0 to 7.0.13

Discovery Timeline

• Not Available - Vulnerability discovered by Not Available
• Not Available - Responsible disclosure to Fortinet
• Not Available - CVE CVE-2023-50176 assigned
• Not Available - Fortinet releases security patch
• 2024-11-12 - CVE CVE-2023-50176 published to NVD
• 2024-12-12 - Last updated in NVD database

Technical Details for CVE-2023-50176

Vulnerability Analysis

The session fixation vulnerability enables attackers to craft a phishing attack using an improperly invalidated session ID. This can be used to execute commands with unauthorized privileges.

Root Cause

The root cause of this vulnerability is improper session management, allowing attackers to set and leverage session IDs for unauthorized access.

Attack Vector

Attackers exploit this vulnerability through a network-based attack by sending a phishing link incorporating a pre-determined session identifier.

// Example exploitation code (sanitized)
fetch('https://targeted-forti-os-instance/session/auth', {
    method: 'POST',
    credentials: 'include',
    body: JSON.stringify({
        "session_id": "malicious-session-id"
    })
});

Detection Methods for CVE-2023-50176

Indicators of Compromise

• Unusual session activity
• Suspicious entries in authentication logs
• Anomalous use of SAML authentication

Detection Strategies

Deploy advanced log monitoring solutions with a focus on SAML authentication processes and session activities. Utilize anomaly detection analytics to identify unexpected session behaviors.

Monitoring Recommendations

Enable detailed auditing for authentication events. Implement network traffic analysis to monitor suspicious phishing links.

How to Mitigate CVE-2023-50176

Immediate Actions Required

• Issue updated user guidance regarding phishing risks
• Engage users in security awareness training focusing on recognizing and reporting phishing attempts
• Implement additional authentication checks for session IDs

Patch Information

Regularly review Fortinet's advisory page at Fortinet Advisory for the latest security patches and updates.

Workarounds

Configure session management policies to invalidate existing session IDs upon re-authentication and conduct a session cleanup regularly.

# Configuration example
echo "Disabling weak session IDs"
sudo fortios-cli session-settings update --invalidate-weak-ids