CVE-2026-4537: Cudy TR1200 RCE Vulnerability

CVE-2026-4537 Overview

A command injection vulnerability has been identified in the Cudy TR1200 router, specifically in firmware version R46-2.4.15-20250721-164017. The vulnerability exists in the action_ipsec_conn function within the file /usr/bin/lib/lua/luci/controller/ipsec.lua. This flaw allows remote authenticated attackers to inject and execute arbitrary operating system commands through manipulation of user-controlled input parameters.

Critical Impact
Remote attackers with administrative access can execute arbitrary commands on the affected device, potentially leading to complete device compromise, network pivoting, or persistent backdoor installation.

Affected Products

Cudy TR1200 Router with firmware version R46-2.4.15-20250721-164017
Cudy TR1200 devices running vulnerable LuCI web interface

Discovery Timeline

2026-03-22 - CVE-2026-4537 published to NVD
2026-03-23 - Last updated in NVD database

Technical Details for CVE-2026-4537

Vulnerability Analysis

This vulnerability is classified as CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), commonly known as injection. The affected function action_ipsec_conn in the LuCI web interface controller fails to properly sanitize user-supplied input before passing it to system command execution routines.

The Cudy TR1200 router uses the LuCI web interface framework, which is commonly deployed on OpenWrt-based devices. The IPsec configuration handler in /usr/bin/lib/lua/luci/controller/ipsec.lua accepts user input that is subsequently used in command execution without adequate input validation or sanitization. This allows an authenticated attacker with administrative privileges to inject shell metacharacters or additional commands that will be executed with the privileges of the web server process, typically root on embedded devices.

The exploit has been publicly disclosed, making it essential for organizations using this device to take immediate action. The vendor was contacted regarding this vulnerability but did not respond.

Root Cause

The root cause of this vulnerability stems from insufficient input validation in the action_ipsec_conn function. The LuCI controller accepts user-controlled parameters for IPsec connection configuration without properly escaping or sanitizing shell metacharacters. When these parameters are concatenated into system commands, attackers can break out of the intended command context and inject arbitrary commands.

This is a common vulnerability pattern in embedded device web interfaces where Lua-based controllers directly invoke system utilities using functions like os.execute() or io.popen() with unsanitized user input.

Attack Vector

The attack can be launched remotely over the network by an authenticated attacker with administrative privileges on the router's web interface. The attacker would navigate to the IPsec configuration functionality and submit specially crafted input containing command injection payloads.

The vulnerability allows manipulation through the IPsec connection configuration interface. An attacker with valid administrative credentials could inject shell commands by including metacharacters such as semicolons, backticks, or pipe operators within IPsec configuration parameters. These injected commands would then be executed by the underlying operating system.

For technical details on the exploitation methodology, refer to the GitHub Command Injection Report.

Detection Methods for CVE-2026-4537

Indicators of Compromise

Unexpected outbound network connections from the router to external hosts
Modified system files or configurations on the router filesystem
Unusual processes running on the device beyond normal router operations
Authentication logs showing access to IPsec configuration endpoints followed by anomalous system behavior

Detection Strategies

Monitor web interface access logs for suspicious requests to /luci/controller/ipsec.lua endpoints containing shell metacharacters
Implement network-level inspection for HTTP POST requests to IPsec configuration pages with unusual parameter values
Deploy integrity monitoring on critical router configuration files to detect unauthorized modifications
Review authentication logs for brute force attempts targeting administrative accounts

Monitoring Recommendations

Enable comprehensive logging on the router's web interface if supported by the firmware
Implement network traffic analysis at the perimeter to detect command-and-control traffic originating from the router
Set up alerts for administrative login attempts from unexpected IP addresses or at unusual times
Monitor for DNS queries or network connections that deviate from the router's normal operational profile

How to Mitigate CVE-2026-4537

Immediate Actions Required

Restrict administrative access to the router's web interface to trusted networks only
Change default administrative credentials and implement strong, unique passwords
Disable remote administration if not required for operational purposes
Consider placing the router behind a firewall or VPN that limits access to management interfaces

Patch Information

As of the last update on 2026-03-23, no vendor patch has been released. The vendor was contacted about this disclosure but did not respond. Organizations should monitor the VulDB entry and vendor channels for any future security updates.

In the absence of an official patch, organizations should implement the workarounds and compensating controls listed below to reduce risk exposure.

Workarounds

Implement network segmentation to isolate the affected router from critical network segments
Use firewall rules to restrict access to the router's web management interface to specific trusted IP addresses only
If IPsec functionality is not required, consider disabling it through the web interface to reduce the attack surface
Deploy a network intrusion detection system (IDS) to monitor for exploitation attempts targeting this vulnerability

bash

# Example firewall rule to restrict management access (iptables)
# Allow management access only from trusted admin network
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP