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CVE-2025-9791: Critical Vulnerability in Tenda AC20 16.03.08.05 Leading to Potential System Compromise

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Overview

A significant weakness has been identified in Tenda AC20 16.03.08.05, a popular wireless router firmware. This vulnerability, designated as CVE-2025-9791, has far-reaching implications and could potentially lead to system compromise or data leakage. This issue particularly affects the file /goform/fromAdvSetMacMtuWan, which due to a flaw, could be manipulated to trigger a buffer overflow. It is an alarming revelation since remote exploitation of this vulnerability is possible, and the exploit has already been made publicly available.

Vulnerability Summary

CVE ID: CVE-2025-9791
Severity: High (CVSS: 8.8)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System compromise and potential data leakage

Affected Products

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Product | Affected Versions

Tenda AC20 | 16.03.08.05

How the Exploit Works

The exploit works by manipulating the argument wanMTU in the /goform/fromAdvSetMacMtuWan file. By doing this, a stack-based buffer overflow is triggered. Buffer overflows are caused when more data is written to a piece of memory or a buffer than it can handle. This overflow of data can then overwrite adjacent memory spaces, causing unpredictable behavior such as crashes, incorrect results, and in this case, potentially granting unauthorized access to the system’s resources.

Conceptual Example Code

This is a conceptual example of how an HTTP request could be used to exploit this vulnerability. The “malicious_payload” would be specifically designed to trigger the buffer overflow.

POST /goform/fromAdvSetMacMtuWan HTTP/1.1
Host: target.example.com
Content-Type: application/json
{ "wanMTU": "malicious_payload" }

Please note this is a simplified representation and in a real-world scenario, the malicious payload would be specially crafted data that would cause the buffer overflow.
In conclusion, it is of utmost importance that users of the affected Tenda AC20 firmware version update to a patched version as soon as possible or apply a suitable WAF/IDS to mitigate the risk temporarily.

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Disclaimer:

The information and code presented in this article are provided for educational and defensive cybersecurity purposes only. Any conceptual or pseudocode examples are simplified representations intended to raise awareness and promote secure development and system configuration practices.

Do not use this information to attempt unauthorized access or exploit vulnerabilities on systems that you do not own or have explicit permission to test.

Ameeba and its authors do not endorse or condone malicious behavior and are not responsible for misuse of the content. Always follow ethical hacking guidelines, responsible disclosure practices, and local laws.

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