Overview
A serious vulnerability has been discovered in the Tenda AC9 router (version 15.03.02.13), which, if exploited, could lead to a system compromise or data leakage. This vulnerability was found in the HTTP POST Request Handler component, specifically in the formSetSafeWanWebMan function of the /goform/SetRemoteWebCfg file. The vulnerability is particularly concerning because it can be exploited remotely, meaning that attackers do not have to be physically present or connected to the same network as the router. Therefore, it is of paramount importance for users of the Tenda AC9 router to understand the implications of this vulnerability and take immediate steps to mitigate the risk.
Vulnerability Summary
CVE ID: CVE-2025-5847
Severity: Critical (8.8 CVSS score)
Attack Vector: Remote
Privileges Required: None
User Interaction: None
Impact: Potential system compromise or data leakage
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Product | Affected Versions
Tenda AC9 Router | 15.03.02.13
How the Exploit Works
The vulnerability stems from a stack-based buffer overflow that occurs when the remoteIp argument in the HTTP POST Request Handler is manipulated. By sending a specially crafted HTTP POST request, an attacker can overflow the buffer, leading to unexpected behavior from the router. This behavior could range from causing the router to crash to allowing the execution of arbitrary code, providing the attacker with unauthorized access to the system or data.
Conceptual Example Code
Below is a conceptual example of how the vulnerability might be exploited. This is a sample HTTP POST request:
POST /goform/SetRemoteWebCfg HTTP/1.1
Host: vulnerable.router
Content-Type: application/x-www-form-urlencoded
remoteIp=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA...In this example, the `remoteIp` value is filled with an excessive number of ‘A’ characters, causing a buffer overflow. This is a simplified example, and actual exploitation would likely involve a more complex payload designed to take advantage of the overflow to execute arbitrary code.
Please note that this code is provided for educational purposes only; attempting to exploit vulnerabilities without permission is illegal and unethical.
Mitigation Guidance
Users of the affected Tenda AC9 router are strongly advised to apply the vendor-provided patch to fix this vulnerability as soon as it is available. In the interim, a web application firewall (WAF) or intrusion detection system (IDS) can provide temporary mitigation against potential exploits.