Compliance Impact

The vulnerability allows authenticated attackers to perform command injection with root privileges on the affected Tenda G103 device, potentially leading to full device compromise.

Such a compromise could result in unauthorized access to sensitive data or disruption of device functionality, which may impact compliance with standards and regulations like GDPR or HIPAA that require protection of personal and sensitive information.

However, the provided information does not explicitly detail the direct effects on compliance with these standards.

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Mitigation Strategies

To mitigate the CVE-2026-5338 vulnerability, immediate steps include restricting access to the affected Tenda G103 device to trusted and authenticated users only, as exploitation requires valid authentication tokens.

Avoid exposing the device's management interface to untrusted networks or the internet to reduce the risk of remote exploitation.

Monitor and review authentication logs for suspicious activity that could indicate attempts to exploit the command injection vulnerability.

Apply any available patches or updates from the vendor that address the improper sanitization of the lanIp parameter in the system.lua file.

If patches are not available, consider implementing network-level controls such as firewall rules to limit access to the vulnerable endpoint.

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Executive Summary

CVE-2026-5338 is a command injection vulnerability found in the Tenda G103 GPON optical network terminals, specifically in the function action_set_system_settings within the system.lua file.

The vulnerability arises because the lanIp parameter is not properly sanitized before being used in system commands. This allows an authenticated attacker to inject arbitrary shell commands by including special characters like backticks, semicolons, or logical AND operators in the lanIp argument.

Exploiting this flaw enables execution of commands with root privileges, potentially compromising the entire device. The attack requires valid authentication tokens and cookies, meaning only authenticated users can perform it.

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Impact Analysis

This vulnerability can lead to full device compromise because attackers can execute arbitrary commands with root privileges on the affected Tenda G103 device.

An attacker who successfully exploits this flaw can manipulate system settings, install malware, disrupt network operations, or gain persistent unauthorized access.

Since the attack requires authentication, it mainly impacts users or administrators with access credentials, but the consequences can be severe including loss of control over the device and potential network security breaches.

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Detection Guidance

This vulnerability can be detected by attempting to exploit the command injection in the lanIp parameter of the action_set_system_settings function. A common detection method is to send a crafted POST request to the endpoint /cgi-bin/luci/;stok=<session_token>/admin/system/set_system_settings with a payload that includes shell metacharacters to test for command injection.

• Send a POST request with payload: lanIp=1`touch$IFS/tmp/setting.txt` to check if the file /tmp/setting.txt is created on the device.
• Verify the presence of the /tmp/setting.txt file on the device to confirm successful command injection.

Note that exploitation requires valid authentication tokens and cookies, so detection commands must be run with authenticated access.

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