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.
