CVE-2024-23106: Fortinet FortiClientEMS Auth Bypass Flaw

CVE-2024-23106 Overview

CVE-2024-23106 is a critical authentication vulnerability in Fortinet FortiClientEMS that allows improper restriction of excessive authentication attempts (CWE-307). This vulnerability enables unauthenticated attackers to perform brute force attacks against the FortiClientEMS management console through crafted HTTP or HTTPS requests, potentially compromising administrative credentials and gaining unauthorized access to the endpoint management system.

Critical Impact

Unauthenticated attackers can exploit this vulnerability to perform brute force attacks against the FortiClientEMS console, potentially gaining administrative access to the enterprise endpoint management infrastructure without any prior authentication requirements.

Affected Products

• Fortinet FortiClientEMS version 7.2.0 through 7.2.4
• Fortinet FortiClientEMS versions before 7.0.10

Discovery Timeline

• 2025-01-14 - CVE-2024-23106 published to NVD
• 2025-07-16 - Last updated in NVD database

Technical Details for CVE-2024-23106

Vulnerability Analysis

This vulnerability stems from missing or inadequate rate limiting on authentication endpoints within FortiClientEMS. The management console fails to properly restrict the number of authentication attempts that can be made within a given timeframe, violating secure authentication best practices defined in CWE-307 (Improper Restriction of Excessive Authentication Attempts).

FortiClientEMS serves as a centralized endpoint management solution for FortiClient deployments across enterprise environments. The management console provides administrative access to configure, monitor, and manage security policies across all connected endpoints. When an attacker can perform unlimited authentication attempts, they can systematically test credential combinations until valid credentials are discovered.

The network-accessible nature of this vulnerability is particularly concerning as it requires no prior authentication, no user interaction, and can be exploited with low complexity. Successful exploitation grants attackers the same level of access as legitimate administrators, potentially affecting the confidentiality, integrity, and availability of managed endpoints across the enterprise.

Root Cause

The root cause of CVE-2024-23106 is the absence of authentication throttling mechanisms in the FortiClientEMS console. The application fails to implement account lockout policies, progressive delays between authentication attempts, or CAPTCHA challenges after repeated failed login attempts. This design oversight allows attackers to submit authentication requests at high rates without being blocked or rate-limited.

Attack Vector

The attack vector for this vulnerability is network-based, targeting the FortiClientEMS web console's HTTP/HTTPS authentication endpoints. An attacker can exploit this vulnerability by sending a high volume of crafted authentication requests to the management console, systematically testing username and password combinations. Common attack tools like Hydra, Burp Suite Intruder, or custom scripts can automate this process, testing thousands of credential combinations per minute against exposed FortiClientEMS instances.

The attack does not require any prior access or authentication, making any internet-exposed or network-accessible FortiClientEMS console a potential target. Organizations with weak password policies or default credentials are at heightened risk of successful exploitation.

Detection Methods for CVE-2024-23106

Indicators of Compromise

• High volume of failed authentication attempts against FortiClientEMS console from single or multiple source IP addresses
• Unusual login patterns including rapid sequential authentication requests
• Successful authentication following numerous failed attempts from the same source
• Authentication attempts using common username lists (admin, administrator, root, forticlient)
• Network traffic anomalies on ports associated with FortiClientEMS management interface

Detection Strategies

• Implement network-level monitoring for excessive connection attempts to FortiClientEMS management ports
• Configure SIEM rules to alert on authentication failure thresholds within defined timeframes
• Deploy intrusion detection signatures for HTTP/HTTPS brute force patterns targeting known FortiClientEMS authentication endpoints
• Monitor FortiClientEMS logs for repeated authentication failures from external IP ranges

Monitoring Recommendations

• Enable comprehensive logging on FortiClientEMS authentication events including source IP, timestamp, and success/failure status
• Implement real-time alerting for authentication anomalies with automated incident response workflows
• Correlate FortiClientEMS authentication events with network flow data to identify distributed brute force attempts
• Establish baseline authentication patterns to detect deviations indicative of attack activity

How to Mitigate CVE-2024-23106

Immediate Actions Required

• Upgrade FortiClientEMS to version 7.2.5 or later for 7.2.x branch deployments
• Upgrade FortiClientEMS to version 7.0.10 or later for 7.0.x branch deployments
• Restrict network access to FortiClientEMS management console to trusted IP ranges only
• Implement strong password policies and consider multi-factor authentication for console access
• Review authentication logs for evidence of exploitation attempts prior to patching

Patch Information

Fortinet has released security updates to address this vulnerability. Detailed patch information and upgrade instructions are available in the Fortinet PSIRT Advisory FG-IR-23-476. Organizations should prioritize upgrading to FortiClientEMS 7.2.5 or higher, or 7.0.10 or higher depending on their deployment branch.

Workarounds

• Place FortiClientEMS management console behind a VPN or jump server to limit direct network exposure
• Configure external rate limiting via web application firewall (WAF) or reverse proxy to throttle authentication requests
• Implement IP allowlisting at the network or firewall level to restrict console access to known administrator addresses
• Enable account lockout mechanisms if available at the network perimeter layer

# Example: Restrict FortiClientEMS console access via firewall rule (iptables)
# Limit connections to management port from trusted networks only
iptables -A INPUT -p tcp --dport 8013 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 8013 -s 192.168.0.0/16 -j ACCEPT
iptables -A INPUT -p tcp --dport 8013 -j DROP