CVE-2024-9441: Linear eMerge e3-Series RCE Vulnerability

CVE-2024-9441 Overview

CVE-2024-9441 is a critical OS command injection vulnerability affecting the Linear eMerge e3-Series access control systems through version 1.00-07. This vulnerability allows a remote, unauthenticated attacker to execute arbitrary operating system commands by exploiting the login_id parameter within the forgot_password functionality accessible over HTTP. The Linear eMerge e3-Series is a widely deployed building access control platform, making this vulnerability particularly dangerous for physical security infrastructure.

Critical Impact

Remote unauthenticated attackers can achieve complete system compromise through arbitrary OS command execution, potentially gaining full control over physical access control systems and building security infrastructure.

Affected Products

• Linear eMerge e3-Series through version 1.00-07
• Nortek Linear eMerge E3 access control devices

Discovery Timeline

• 2024-10-02 - CVE-2024-9441 published to NVD
• 2024-10-04 - Last updated in NVD database

Technical Details for CVE-2024-9441

Vulnerability Analysis

This vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), commonly known as OS Command Injection. The Linear eMerge e3-Series access control system fails to properly sanitize user-supplied input in the login_id parameter when processing password reset requests.

The forgot_password functionality, designed to help users recover their credentials, accepts the login_id parameter via HTTP requests. Due to insufficient input validation, an attacker can inject shell metacharacters and arbitrary commands that are then executed by the underlying operating system with the privileges of the web application process.

This pre-authentication attack surface is particularly concerning as it requires no credentials or prior access to exploit. The vulnerability enables attackers to potentially compromise the entire access control system, which could have severe implications for physical security.

Root Cause

The root cause of this vulnerability lies in the improper handling of user input within the forgot_password function. The application concatenates the login_id parameter directly into an operating system command without adequate sanitization or escaping of shell metacharacters. This allows special characters such as semicolons, pipes, backticks, or command substitution syntax to be interpreted as command delimiters, enabling injection of arbitrary commands.

Attack Vector

The attack is conducted remotely over the network via HTTP requests to the forgot_password endpoint. An attacker crafts a malicious HTTP request containing shell metacharacters and commands within the login_id parameter. When the server processes this request, the injected commands are executed by the system shell.

The vulnerability mechanism involves the application passing unsanitized user input to system shell functions. When an attacker submits a specially crafted login_id value containing command separators (such as ;, |, or $()) followed by malicious commands, these commands are executed on the target system. For detailed technical analysis and proof-of-concept information, see the SSD Disclosure Advisory and VulnCheck Advisory.

Detection Methods for CVE-2024-9441

Indicators of Compromise

• Unusual HTTP requests to the forgot_password endpoint containing shell metacharacters (;, |, &, `, $()) in the login_id parameter
• Unexpected outbound network connections from Linear eMerge devices
• New processes spawned by the web server process with suspicious command-line arguments
• Modifications to system files, cron jobs, or user accounts on eMerge devices

Detection Strategies

• Monitor HTTP access logs for requests to forgot_password endpoints with suspicious characters in parameters
• Deploy network intrusion detection rules to identify command injection patterns in HTTP traffic
• Implement web application firewall (WAF) rules to block requests containing shell metacharacters in form parameters
• Monitor for anomalous process creation on access control systems

Monitoring Recommendations

• Enable verbose logging on Linear eMerge devices and forward logs to a SIEM for correlation
• Establish baseline network behavior for access control systems and alert on deviations
• Monitor for unauthorized authentication attempts and lateral movement from eMerge device IP addresses
• Regularly audit access control system configurations for unauthorized changes

How to Mitigate CVE-2024-9441

Immediate Actions Required

• Isolate affected Linear eMerge e3-Series devices from direct internet exposure immediately
• Place access control systems behind a properly configured firewall with strict access controls
• Implement network segmentation to limit potential lateral movement from compromised devices
• Enable enhanced logging and monitoring on all affected systems

Patch Information

At the time of this advisory, vendor patch information is not available in the CVE data. Organizations should contact Nortek/Linear directly for security updates and monitor the SSD Disclosure Advisory and VulnCheck Advisory for updated remediation guidance.

Workarounds

• Restrict network access to Linear eMerge devices to trusted IP addresses only using firewall rules
• Disable or block access to the forgot_password functionality if not operationally required
• Deploy a reverse proxy or web application firewall to filter malicious requests before they reach the device
• Consider implementing VPN-only access for administrative functions on access control systems

Network segmentation and access restrictions should be implemented as compensating controls:

# Example iptables rules to restrict access to eMerge device
# Replace 192.168.1.100 with your eMerge device IP
# Replace 10.0.0.0/24 with your trusted management network

# Block all incoming HTTP/HTTPS from untrusted networks
iptables -A INPUT -p tcp --dport 80 -s ! 10.0.0.0/24 -d 192.168.1.100 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 10.0.0.0/24 -d 192.168.1.100 -j DROP

# Allow only from trusted management network
iptables -A INPUT -p tcp --dport 80 -s 10.0.0.0/24 -d 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 10.0.0.0/24 -d 192.168.1.100 -j ACCEPT