Compliance Impact

The vulnerability in Tenda F456 allows remote attackers to execute arbitrary code or cause denial of service via a stack-based buffer overflow. Such unauthorized access or disruption could lead to compromise of sensitive data or system availability.

While the provided information does not explicitly mention compliance with standards like GDPR or HIPAA, exploitation of this vulnerability could potentially result in breaches of confidentiality, integrity, and availability of data, which are core concerns of these regulations.

Therefore, if the affected device processes or stores personal or protected health information, this vulnerability could negatively impact compliance with regulations requiring protection of such data.

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Executive Summary

CVE-2026-6196 is a stack-based buffer overflow vulnerability found in the Tenda F456 router version 1.0.0.5. It occurs in the HTTP daemon's function formexeCommand, which processes a user-supplied parameter called "cmdinput."

The vulnerability arises because the user input is copied into a buffer using the unsafe strcpy function without checking the input length. This allows an attacker to overflow the stack buffer by sending an excessively long "cmdinput" value.

Exploitation is possible remotely by sending a crafted HTTP POST request to the /goform/exeCommand endpoint with a large payload in the "cmdinput" parameter. This can lead to denial of service or remote code execution on the device.

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Impact Analysis

This vulnerability can have serious impacts including denial of service (DoS) and remote code execution (RCE) on the affected Tenda F456 router.

• Denial of Service: An attacker can crash or disrupt the router's operation by exploiting the buffer overflow.
• Remote Code Execution: An attacker may execute arbitrary code remotely, potentially taking full control of the device.
• Compromise of network security and privacy due to unauthorized access or control over the router.

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Detection Guidance

This vulnerability can be detected by sending a crafted HTTP POST request to the endpoint /goform/exeCommand with an excessively long "cmdinput" parameter. The request should include typical HTTP headers and a large payload of repeated characters in the cmdinput field to trigger the stack-based buffer overflow.

A detection command example using curl might be:

• curl -X POST http://<target-ip>/goform/exeCommand -d "cmdinput=$(python3 -c 'print("a"*1000)')" -H "Content-Type: application/x-www-form-urlencoded"

If the device is vulnerable, this request may cause a denial of service or unexpected behavior, indicating the presence of the vulnerability.

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Mitigation Strategies

To mitigate the CVE-2026-6196 vulnerability in the Tenda F456 router version 1.0.0.5, immediate steps include restricting remote access to the device's HTTP service, especially the /goform/exeCommand endpoint, to prevent exploitation.

Additionally, monitoring network traffic for suspicious POST requests with unusually long 'cmdinput' parameters can help detect exploitation attempts.

If possible, apply any available firmware updates or patches from the vendor that address this buffer overflow vulnerability.

As a temporary measure, consider disabling remote management features or placing the device behind a firewall to limit exposure.

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