Overview
A critical vulnerability, classified as CVE-2025-5839, has been identified in Tenda AC9 version 15.03.02.13, a popular router used by many businesses and individuals alike. This vulnerability lies within the POST Request Handler component of the router’s software, specifically, the fromadvsetlanip function of the /goform/AdvSetLanip file. This vulnerability matters because it allows an attacker to remotely manipulate the lanMask argument, causing a buffer overflow, which can potentially lead to system compromise or data leakage. The exploit is public, increasing the risk of its exploitation.
Vulnerability Summary
CVE ID: CVE-2025-5839
Severity: Critical (CVSS score 8.8)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise or data leakage
Affected Products
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Product | Affected Versions
Tenda AC9 | 15.03.02.13
How the Exploit Works
The exploit works by an attacker sending a specially crafted HTTP POST request to the /goform/AdvSetLanip endpoint of the router’s web interface. This request manipulates the lanMask argument, which is not properly validated by the fromadvsetlanip function. This manipulation causes a buffer overflow in the system, which can potentially lead to arbitrary code execution or data leakage.
Conceptual Example Code
POST /goform/AdvSetLanip HTTP/1.1
Host: target.example.com
Content-Type: application/x-www-form-urlencoded
lanMask=255.255.255.0%00{malicious_code_here}In this conceptual example, the malicious code follows a null byte (%00), which is often used to indicate the end of a string in C/C++. If the malicious code is executed, it could compromise the system or cause data leakage.
Protection and Mitigation
The best mitigation strategy for this vulnerability is to apply the patch provided by the vendor as soon as it becomes available. In the meantime, using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can provide temporary mitigation by detecting and blocking malicious traffic. However, these measures are not foolproof, as sophisticated attackers may be able to bypass them. Therefore, applying the vendor’s patch should be a top priority.