Overview
A critical vulnerability, identified as CVE-2025-7551, has been discovered in the Tenda FH1201 1.2.0.14(408) router. This flaw is particularly dangerous as it affects the PPTP VPN functionality of the device, a feature that is frequently used by remote workers or businesses with multiple locations. The vulnerability allows remote manipulation of the username argument to cause a stack-based buffer overflow, potentially leading to system compromise or data leakage.
Vulnerability Summary
CVE ID: CVE-2025-7551
Severity: Critical (8.8 CVSS Score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise or data leakage upon successful exploitation.
Affected Products
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Product | Affected Versions
Tenda FH1201 | 1.2.0.14(408)
How the Exploit Works
The vulnerability resides in the ‘fromPptpUserAdd’ function of the /goform/PPTPDClient file. An attacker can manipulate the ‘modino/username’ argument to overflow the buffer. This overflow could potentially allow the attacker to execute arbitrary code or cause a denial of service through a crafted HTTP request. The vulnerability can be exploited remotely, without any need for user interaction or privileges.
Conceptual Example Code
This is a conceptual example of how the vulnerability might be exploited. An attacker makes an HTTP POST request with a larger than expected ‘username’ value to trigger the buffer overflow.
POST /goform/PPTPDClient?modino/username=AAAAAAAAAA... HTTP/1.1
Host: target-router-ip
Content-Type: application/x-www-form-urlencoded
username=AAAAAAAAAA...&password=attacker-passwordIn this example, ‘AAAAAAAAAA…’ represents an excessively long string designed to overflow the buffer and potentially lead to arbitrary code execution.
Mitigation Guidance
Owners of affected Tenda FH1201 routers are advised to apply the vendor patch as soon as possible to fix this vulnerability. In the absence of a patch, a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can be used as a temporary measure to mitigate the risk. However, these are not failsafe solutions and the patch should be applied as soon as it becomes available. Regularly updating and patching your devices is the most effective way to protect against such vulnerabilities.