CVE-2026-2615: Wavlink WL-NU516U1 Firmware RCE Vulnerability

CVE-2026-2615 Overview

A command injection vulnerability has been identified in the Wavlink WL-NU516U1 network device firmware up to version 20251208. The vulnerability exists in the singlePortForwardDelete function within the /cgi-bin/firewall.cgi file, where improper handling of the del_flag argument allows attackers to inject and execute arbitrary system commands. This flaw can be exploited remotely by authenticated attackers, potentially leading to complete device compromise.

Critical Impact

Successful exploitation allows remote authenticated attackers to execute arbitrary commands on the affected device, potentially leading to full system compromise, data exfiltration, or use of the device as a pivot point for lateral movement within the network.

Affected Products

• Wavlink WL-NU516U1 Firmware (up to version 20251208)
• Wavlink WL-NU516U1 Hardware Device

Discovery Timeline

• 2026-02-17 - CVE-2026-2615 published to NVD
• 2026-02-18 - Last updated in NVD database

Technical Details for CVE-2026-2615

Vulnerability Analysis

This command injection vulnerability (CWE-74) stems from insufficient input validation in the Wavlink WL-NU516U1 firmware's firewall configuration interface. The vulnerable singlePortForwardDelete function processes user-supplied input through the del_flag parameter without proper sanitization, allowing malicious command sequences to be injected and executed by the underlying operating system.

The network-accessible nature of this vulnerability significantly increases its risk profile. While the attack requires high privileges (authenticated access), the lack of any user interaction requirement means that once an attacker has valid credentials, exploitation can be automated. Successful attacks can result in complete compromise of confidentiality, integrity, and availability of the affected device.

Root Cause

The root cause of this vulnerability is improper input validation in the singlePortForwardDelete function located in /cgi-bin/firewall.cgi. The del_flag argument is passed directly to system commands without adequate sanitization or escaping of special characters. This allows shell metacharacters to be interpreted by the system, enabling command injection attacks. The firmware fails to implement proper input validation boundaries or use parameterized command execution methods that would prevent such injection.

Attack Vector

The attack vector is network-based, requiring an authenticated attacker to send crafted HTTP requests to the device's web interface. The attacker must manipulate the del_flag parameter in requests to /cgi-bin/firewall.cgi, injecting shell commands that will be executed by the device's operating system with the privileges of the web server process.

The attack can be launched remotely, though it requires high-level privileges (administrative authentication). Once authenticated, an attacker can craft malicious requests that include command injection payloads within the del_flag parameter, such as command separators (;, |, &) followed by arbitrary system commands.

The vulnerability mechanism involves insufficient sanitization of the del_flag parameter before it is passed to system command execution functions. Attackers can leverage shell metacharacters to break out of the intended command context and execute arbitrary commands. For detailed technical information and proof-of-concept details, refer to the GitHub PoC Repository.

Detection Methods for CVE-2026-2615

Indicators of Compromise

• Unusual HTTP requests to /cgi-bin/firewall.cgi containing shell metacharacters (;, |, &, $(), backticks) in the del_flag parameter
• Unexpected outbound network connections from the Wavlink device to external IP addresses
• Anomalous process execution on the device, particularly shell processes spawned by the web server
• Log entries showing malformed or suspicious requests to the firewall configuration endpoint

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests containing command injection patterns in parameters sent to /cgi-bin/firewall.cgi
• Monitor network traffic for HTTP requests to vulnerable endpoints containing encoded or plaintext shell metacharacters
• Deploy intrusion detection system (IDS) signatures specifically targeting Wavlink firmware command injection attempts
• Enable comprehensive logging on network infrastructure to capture all requests to IoT device management interfaces

Monitoring Recommendations

• Configure network monitoring to alert on any access to the /cgi-bin/firewall.cgi endpoint from unexpected source IP addresses
• Implement behavioral analysis to detect anomalous command execution patterns on IoT devices
• Monitor for unusual DNS queries or outbound connections originating from Wavlink devices that may indicate post-exploitation activity

How to Mitigate CVE-2026-2615

Immediate Actions Required

• Restrict network access to the Wavlink WL-NU516U1 web management interface to trusted administrative IP addresses only
• Place affected devices behind a firewall that blocks external access to the web interface
• Implement strong authentication and consider changing default credentials immediately
• Monitor the device for signs of compromise and review access logs regularly
• Consider network segmentation to isolate IoT devices from critical network infrastructure

Patch Information

As of the last update, the vendor (Wavlink) was contacted about this vulnerability but did not respond. No official patch is currently available. Organizations should monitor the VulDB entry and Wavlink's official channels for any future security updates. Given the lack of vendor response, affected organizations should implement compensating controls immediately.

Workarounds

• Disable remote management access to the device's web interface if not required for operations
• Implement network-level access controls using firewall rules to restrict access to the device's management interface
• Consider deploying a reverse proxy with input validation capabilities in front of the device's web interface
• If possible, isolate the device on a separate VLAN with no direct internet access
• Evaluate replacing the affected device with alternatives from vendors with more responsive security practices

# Example firewall rule to restrict access to Wavlink management interface
# Allow only trusted admin network to access device web interface
iptables -A INPUT -s 192.168.1.0/24 -d WAVLINK_DEVICE_IP -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -d WAVLINK_DEVICE_IP -p tcp --dport 80 -j DROP