CVE-2025-4349: D-Link DIR-600L Firmware RCE Vulnerability

CVE-2025-4349 Overview

A critical command injection vulnerability has been identified in the D-Link DIR-600L wireless router firmware up to version 2.07B01. The vulnerability exists within the formSysCmd function, where improper handling of the host argument allows remote attackers to inject and execute arbitrary system commands. This flaw enables authenticated remote attackers to gain complete control over affected devices, potentially compromising network security and enabling further attacks on connected systems. Notably, this vulnerability affects end-of-life products that are no longer supported by D-Link.

Critical Impact
Remote attackers with low privileges can execute arbitrary commands on vulnerable D-Link DIR-600L routers, potentially leading to complete device compromise, network infiltration, and lateral movement to connected systems.

Affected Products

D-Link DIR-600L Firmware up to version 2.07B01
D-Link DIR-600L Hardware

Discovery Timeline

2025-05-06 - CVE-2025-4349 published to NVD
2025-05-12 - Last updated in NVD database

Technical Details for CVE-2025-4349

Vulnerability Analysis

This command injection vulnerability (CWE-77) affects the formSysCmd function in the D-Link DIR-600L router firmware. The function fails to properly sanitize the host parameter before passing it to system command execution routines. When a user-controlled input is incorporated into a shell command without adequate validation, attackers can break out of the intended command context and execute arbitrary system commands.

The vulnerability is remotely exploitable over the network without requiring user interaction. While it does require low-level authentication, the attack complexity is low, making this an accessible target for malicious actors. Successful exploitation grants attackers high-level access to confidentiality, integrity, and availability of the affected device.

Root Cause

The root cause of this vulnerability is improper input validation (CWE-74) in the formSysCmd function. The function accepts user-supplied input through the host argument and passes it directly to shell command execution without proper sanitization or escaping of special characters. This allows attackers to inject shell metacharacters and command separators to append or chain additional commands that execute with the privileges of the web server process running on the router.

Attack Vector

The attack vector for CVE-2025-4349 is network-based, allowing remote exploitation. An attacker with valid credentials can craft malicious HTTP requests to the vulnerable formSysCmd endpoint, injecting shell commands through the host parameter. The injected commands execute on the underlying Linux-based operating system with the privileges of the web application, typically root on embedded devices like routers.

The vulnerability mechanism works as follows: user input intended for diagnostic functions (such as ping or traceroute) is concatenated into a shell command string without sanitization. By inserting shell metacharacters like semicolons (;), pipes (|), or command substitution operators, attackers can terminate the intended command and append arbitrary commands.

For technical details and proof-of-concept information, refer to the GitHub D-Link Command Injection PoC.

Detection Methods for CVE-2025-4349

Indicators of Compromise

Unexpected outbound network connections from the router to unknown external IP addresses
Modified configuration files or firmware on the D-Link DIR-600L device
Unusual log entries showing malformed or suspicious requests to the formSysCmd endpoint
Evidence of shell command execution patterns containing semicolons, pipes, or backticks in HTTP request logs

Detection Strategies

Monitor network traffic for suspicious HTTP requests targeting D-Link router management interfaces
Implement intrusion detection rules to identify command injection patterns in HTTP POST parameters
Review router logs for anomalous activity or authentication attempts
Deploy network segmentation to isolate IoT devices and routers from critical network segments

Monitoring Recommendations

Enable logging on network perimeter devices to capture traffic to and from D-Link router management ports
Implement SIEM rules to alert on command injection attack patterns targeting embedded device management interfaces
Conduct periodic firmware version audits to identify vulnerable D-Link DIR-600L devices on the network
Monitor for DNS queries or network traffic to known malicious infrastructure from router IP addresses

How to Mitigate CVE-2025-4349

Immediate Actions Required

Identify and inventory all D-Link DIR-600L devices on your network
Restrict management interface access to trusted internal networks only
Implement strong firewall rules to block external access to router administration interfaces
Consider replacing end-of-life D-Link DIR-600L devices with actively supported router models

Patch Information

D-Link has indicated that the DIR-600L is an end-of-life product and is no longer receiving security updates. There is no official patch available from D-Link for this vulnerability. Organizations using affected devices should prioritize device replacement with currently supported products. For additional information, visit the D-Link Official Website.

Workarounds

Disable remote management features on the D-Link DIR-600L router
Restrict access to the router's web management interface using MAC address filtering or IP allowlists
Place vulnerable devices behind a properly configured firewall that blocks access to management ports from untrusted networks
Implement network segmentation to isolate vulnerable routers from sensitive network segments

bash

# Example firewall rule to restrict router management access (iptables)
# Block external access to common router management ports
iptables -A INPUT -i eth0 -p tcp --dport 80 -s !192.168.1.0/24 -j DROP
iptables -A INPUT -i eth0 -p tcp --dport 443 -s !192.168.1.0/24 -j DROP
iptables -A INPUT -i eth0 -p tcp --dport 8080 -s !192.168.1.0/24 -j DROP