CVE-2024-9137: Moxa Service Authentication Bypass Flaw

CVE-2024-9137 Overview

CVE-2024-9137 is a missing authentication vulnerability affecting Moxa routers, network security appliances, and Ethernet switches. The affected products lack an authentication check when sending commands to the server via the Moxa service. This vulnerability allows an attacker to execute specified commands, potentially leading to unauthorized downloads or uploads of configuration files and complete system compromise.

Critical Impact

Unauthenticated remote attackers can execute arbitrary commands on affected Moxa devices, enabling configuration tampering, data exfiltration, and full device compromise without requiring any credentials.

Affected Products

• Moxa Routers (see MPSA-241154 advisory for specific models)
• Moxa Network Security Appliances (see MPSA-241154 advisory for specific models)
• Moxa Ethernet Switches (see MPSA-241156 advisory for specific models)

Discovery Timeline

• October 14, 2024 - CVE-2024-9137 published to NVD
• January 17, 2025 - Last updated in NVD database

Technical Details for CVE-2024-9137

Vulnerability Analysis

This vulnerability is classified under CWE-306 (Missing Authentication for Critical Function). The core issue lies in the Moxa service failing to implement proper authentication checks before processing incoming commands. When commands are sent to the server via the Moxa service interface, the system accepts and executes them without verifying the identity or authorization level of the requesting entity.

The lack of authentication creates a direct pathway for attackers to interact with critical device functions. This includes the ability to download existing configuration files, upload malicious configurations, and execute system-level commands that could lead to complete device takeover.

Root Cause

The root cause of CVE-2024-9137 is the absence of authentication mechanisms in the Moxa service command processing workflow. The service is designed to accept and process commands from network sources but fails to implement any form of credential verification, session validation, or access control checks before executing requested operations. This design flaw allows any network-reachable attacker to interact with the service as if they were an authenticated administrator.

Attack Vector

The attack vector for this vulnerability is network-based. An attacker with network access to the affected Moxa device can send specially crafted commands directly to the Moxa service without providing any authentication credentials. The exploitation process involves:

1. Identifying a network-accessible Moxa device running the vulnerable service
2. Connecting to the Moxa service endpoint
3. Sending commands to download device configuration files containing sensitive information
4. Uploading modified configuration files to alter device behavior
5. Executing additional commands to establish persistent access or pivot to other network resources

The attack requires no user interaction and can be performed by any network-adjacent attacker or remotely if the device is exposed to the internet. The vulnerability enables both integrity and availability impacts through unauthorized configuration changes and potential denial of service conditions.

Detection Methods for CVE-2024-9137

Indicators of Compromise

• Unexpected configuration file downloads or uploads to/from Moxa devices
• Unusual network connections to Moxa service ports from unauthorized IP addresses
• Configuration changes on Moxa devices without corresponding administrator activity logs
• Presence of unauthorized user accounts or modified access credentials on affected devices

Detection Strategies

• Monitor network traffic for unauthenticated command sequences targeting Moxa service ports
• Implement network segmentation monitoring to detect lateral movement from compromised OT/ICS devices
• Deploy intrusion detection systems with signatures for known Moxa service exploitation patterns
• Establish baseline configuration monitoring with alerts for unauthorized changes

Monitoring Recommendations

• Enable comprehensive logging on all Moxa devices and forward logs to a centralized SIEM
• Monitor for connection attempts to Moxa devices from non-administrative network segments
• Implement file integrity monitoring for device configuration files
• Conduct regular configuration audits comparing current state against known-good baselines

How to Mitigate CVE-2024-9137

Immediate Actions Required

• Review the Moxa security advisories MPSA-241154 and MPSA-241156 to identify affected device models
• Isolate affected Moxa devices from untrusted network segments immediately
• Apply firmware updates from Moxa that address this vulnerability
• Audit device configurations for signs of tampering or unauthorized access

Patch Information

Moxa has released security advisories addressing this vulnerability. Affected users should consult MPSA-241154 for routers and network security appliances, and MPSA-241156 for Ethernet switches. These advisories contain specific firmware versions and download links for patched releases. Organizations should prioritize applying the latest firmware updates as soon as possible.

Workarounds

• Implement network segmentation to restrict access to Moxa devices to authorized management networks only
• Deploy firewall rules to block external access to Moxa service ports
• Use VPN or other secure tunneling mechanisms for remote management of Moxa devices
• Enable and monitor device-level access logging where available to detect unauthorized access attempts

# Example firewall rule to restrict Moxa service access (iptables)
# Replace MOXA_SERVICE_PORT with the actual port number
# Replace MANAGEMENT_SUBNET with your authorized management network
iptables -A INPUT -p tcp --dport MOXA_SERVICE_PORT -s MANAGEMENT_SUBNET -j ACCEPT
iptables -A INPUT -p tcp --dport MOXA_SERVICE_PORT -j DROP