CVE-2025-4139: Critical Buffer Overflow Vulnerability in Netgear EX6120 1.0.0.68

Overview

In our continuously evolving digital world, security vulnerabilities pose a significant threat to both individuals and businesses alike. One such recent discovery is the critical vulnerability identified in Netgear EX6120 1.0.0.68, a widely used network product. The vulnerability, classified as CVE-2025-4139, has been found in the fwAcosCgiInbound function and can lead to a buffer overflow. This vulnerability has substantial implications, including potential system compromise and data leakage.
The vulnerability CVE-2025-4139 matters because it can be exploited remotely, putting a vast number of systems at risk. Unfortunately, the vendor has been unresponsive to this disclosure, making immediate mitigation efforts crucial for all affected systems.

Vulnerability Summary

CVE ID: CVE-2025-4139
Severity: Critical (8.8/10 CVSS Score)
Attack Vector: Remote
Privileges Required: None
User Interaction: None
Impact: System compromise and potential data leakage

Affected Products

Product | Affected Versions

Netgear EX6120 | 1.0.0.68

How the Exploit Works

The exploit works by manipulating the ‘host’ argument in the fwAcosCgiInbound function of the Netgear EX6120 1.0.0.68. This manipulation allows a buffer overflow to occur. A buffer overflow is a situation where more data is written into a fixed-length buffer than the buffer can handle. This overflow in memory can overwrite adjacent memory locations and cause unpredictable system behavior, including crashes, incorrect execution, and most critically, the execution of malicious code.

Conceptual Example Code

Below is a conceptual example illustrating how the vulnerability might be exploited. This is a sample HTTP request that includes a malicious payload designed to trigger the buffer overflow.

POST /fwAcosCgiInbound HTTP/1.1
Host: vulnerable-router.example.com
Content-Type: application/json
{ "host": "..." } // Insert malicious payload here that overflows the buffer

It should be noted that this is a conceptual example. Real-world exploits may be more complex and require deeper understanding of the system’s internals.

Countermeasures and Mitigation

Until the vendor releases a patch, it’s advisable to use a Web Application Firewall (WAF) or Intrusion Detection System (IDS) as a temporary mitigation method. These measures can detect and prevent the exploitation of the vulnerability. It is always important to keep systems up to date with the latest security patches and updates to ensure maximum protection against such threats.