CVE-2024-0299: Totolink N200RE Firmware RCE Vulnerability

CVE-2024-0299 Overview

A critical OS command injection vulnerability has been identified in the Totolink N200RE router firmware version 9.3.5u.6139_B20201216. The vulnerability exists in the setTracerouteCfg function within the /cgi-bin/cstecgi.cgi file, where improper handling of the command argument allows remote attackers to inject and execute arbitrary operating system commands. This vulnerability can be exploited remotely without authentication, potentially leading to complete device compromise.

Critical Impact

Remote attackers can achieve full control of the affected Totolink N200RE router through unauthenticated OS command injection, potentially enabling network infiltration, traffic interception, and lateral movement.

Affected Products

• Totolink N200RE Firmware version 9.3.5u.6139_B20201216
• Totolink N200RE Hardware

Discovery Timeline

• 2024-01-08 - CVE-2024-0299 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-0299

Vulnerability Analysis

This command injection vulnerability affects the traceroute configuration functionality of Totolink N200RE routers. The setTracerouteCfg function within the CGI handler (/cgi-bin/cstecgi.cgi) fails to properly sanitize user-supplied input in the command parameter before passing it to the underlying operating system for execution. This lack of input validation allows attackers to append or inject arbitrary shell commands that are executed with the privileges of the web server process, typically root on embedded devices.

The exploit has been publicly disclosed, significantly increasing the risk of attacks against vulnerable devices. The vendor was contacted about this vulnerability but did not respond, meaning no official patch is available.

Root Cause

The root cause of CVE-2024-0299 is a classic CWE-78 (Improper Neutralization of Special Elements used in an OS Command) vulnerability. The setTracerouteCfg function directly incorporates user input from the command parameter into system calls without proper sanitization or escaping of shell metacharacters. This allows attackers to break out of the intended command context and execute arbitrary commands.

Attack Vector

The attack can be launched remotely over the network against the router's web management interface. An attacker sends a crafted HTTP request to the /cgi-bin/cstecgi.cgi endpoint, targeting the setTracerouteCfg function with a malicious command parameter containing shell metacharacters and injected commands. Since no authentication appears to be required for exploitation, any attacker with network access to the management interface can exploit this vulnerability.

The vulnerability manifests in the traceroute configuration handler where user-supplied input is passed to OS command execution functions without adequate sanitization. Technical details and proof-of-concept information can be found in the GitHub PoC Documentation and VulDB advisory.

Detection Methods for CVE-2024-0299

Indicators of Compromise

• Unexpected HTTP requests to /cgi-bin/cstecgi.cgi containing the setTracerouteCfg function call
• Shell metacharacters (;, |, &, $(), backticks) present in web server access logs targeting CGI endpoints
• Unusual outbound network connections from the router to unknown IP addresses
• Unexpected processes running on the router device

Detection Strategies

• Monitor web server access logs for requests to /cgi-bin/cstecgi.cgi with suspicious command parameter values
• Deploy network intrusion detection rules to identify command injection patterns targeting Totolink devices
• Implement egress filtering to detect command-and-control communications from compromised routers
• Perform regular firmware integrity checks to detect unauthorized modifications

Monitoring Recommendations

• Enable verbose logging on the router if available and forward logs to a centralized SIEM
• Monitor for unexpected configuration changes or new user accounts on the device
• Track network traffic anomalies from router management interfaces
• Review device behavior for signs of cryptocurrency mining or botnet participation

How to Mitigate CVE-2024-0299

Immediate Actions Required

• Restrict access to the router's web management interface to trusted networks only using firewall rules
• Disable remote management access from WAN interfaces if enabled
• Place vulnerable routers behind a VPN or additional firewall that can filter malicious requests
• Consider replacing affected devices with actively maintained alternatives if no patch becomes available

Patch Information

No official patch is currently available from Totolink. The vendor was contacted about this vulnerability but did not respond. Organizations should implement compensating controls and monitor for any future firmware updates from the vendor.

Workarounds

• Implement network segmentation to isolate vulnerable routers from critical network segments
• Use access control lists (ACLs) to limit which IP addresses can access the router management interface
• Deploy a web application firewall (WAF) in front of the management interface to filter command injection attempts
• Monitor the device closely for signs of compromise and be prepared to restore from a known-good configuration

# Example: Restrict management access using iptables on upstream firewall
# Block external access to router management interface
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -i eth0 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -i eth0 -j DROP

# Allow only specific trusted management IP
iptables -A FORWARD -s 10.0.0.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT