CVE-2026-8188: Wavlink WL-NU516U1 Firmware RCE Vulnerability

CVE-2026-8188 Overview

CVE-2026-8188 is an operating system (OS) command injection vulnerability in the Wavlink NU516U1 wireless router running firmware version M16U1_V240425. The flaw resides in the change_wifi_password function within /cgi-bin/adm.cgi. Attackers can manipulate the wl_channel, wl_Pass, or EncrypType parameters to inject arbitrary operating system commands [CWE-77]. The vulnerability is remotely exploitable and the exploit details have been publicly disclosed. The vendor was contacted prior to disclosure but the affected firmware remains in scope.

Critical Impact
Authenticated attackers can inject arbitrary OS commands through the Wi-Fi password change endpoint, gaining command execution on the router.

Affected Products

Wavlink WL-NU516U1 router (hardware)
Wavlink WL-NU516U1 firmware version M16U1_V240425
Administrative web interface (/cgi-bin/adm.cgi)

Discovery Timeline

2026-05-09 - CVE-2026-8188 published to NVD
2026-05-13 - Last updated in NVD database

Technical Details for CVE-2026-8188

Vulnerability Analysis

The vulnerability exists in the change_wifi_password handler exposed through the CGI endpoint /cgi-bin/adm.cgi. This handler accepts user-supplied input via the wl_channel, wl_Pass, and EncrypType parameters when an administrator updates wireless settings. The application passes these values into an underlying shell command without sanitization or proper argument quoting. As a result, shell metacharacters injected into any of the three parameters are interpreted by the operating system shell rather than treated as literal data.

Successful exploitation grants execution of arbitrary commands within the context of the router's web server process, which typically runs with elevated privileges on embedded Linux devices. This level of access can be used to modify device configuration, intercept network traffic, pivot into the internal network, or deploy persistent malware on the router.

Root Cause

The root cause is improper neutralization of special elements used in an OS command [CWE-77]. The change_wifi_password function concatenates attacker-controlled parameter values directly into a shell command string. There is no input validation, character allowlisting, or use of safe execution APIs that separate command arguments from the command itself.

Attack Vector

The attack vector is network-based and requires low-privileged authenticated access to the administrative interface. An attacker submits a crafted HTTP request to /cgi-bin/adm.cgi invoking the change_wifi_password action with shell metacharacters such as ;, |, `, or $(...) embedded in the wl_channel, wl_Pass, or EncrypType fields. The injected command is executed by the router's shell during the password change routine. Technical exploitation details have been published in the GitHub Vulnerability Report and on VulDB entry 362340.

Detection Methods for CVE-2026-8188

Indicators of Compromise

HTTP POST requests to /cgi-bin/adm.cgi containing shell metacharacters (;, |, &, `, $() within the wl_channel, wl_Pass, or EncrypType parameters.
Unexpected outbound connections originating from the router's management IP address.
Unauthorized changes to wireless configuration, DNS settings, or firmware on the affected device.

Detection Strategies

Inspect web proxy and router access logs for requests targeting the change_wifi_password action with non-standard characters in wireless parameters.
Compare router configuration baselines against current state to identify unauthorized command execution artifacts.
Monitor for new processes or persistence mechanisms on devices where shell access is available through SSH or serial console.

Monitoring Recommendations

Place vulnerable Wavlink devices behind a segmented management VLAN and log all administrative HTTP traffic.
Forward router syslog data to a centralized logging platform for retention and correlation.
Alert on authentication events to the router followed by configuration-change requests containing unusual payloads.

How to Mitigate CVE-2026-8188

Immediate Actions Required

Restrict access to the router's administrative interface to trusted management hosts only and block exposure to the internet.
Rotate the administrative credentials on all Wavlink WL-NU516U1 devices and disable any shared or default accounts.
Audit recent administrative requests to /cgi-bin/adm.cgi for signs of exploitation attempts.

Patch Information

No vendor patch is referenced in the NVD record at the time of publication. Consult the Wavlink support site for firmware updates superseding M16U1_V240425 and apply them as soon as they become available. Where no fix is available, consider replacing the device with a supported model.

Workarounds

Disable remote administration and limit the management interface to a dedicated, firewalled subnet.
Enforce strong, unique administrator passwords and remove any unused administrative accounts to reduce the population of users who can reach the vulnerable endpoint.
Place the device behind a network-layer access control list that drops HTTP requests to /cgi-bin/adm.cgi from untrusted sources.

bash

# Example: restrict access to the router management interface using iptables on an upstream gateway
iptables -A FORWARD -p tcp -d 192.0.2.1 --dport 80 \
  -m iprange ! --src-range 10.10.10.10-10.10.10.20 -j DROP
iptables -A FORWARD -p tcp -d 192.0.2.1 --dport 443 \
  -m iprange ! --src-range 10.10.10.10-10.10.10.20 -j DROP