CVE-2025-4348: Critical Buffer Overflow Vulnerability in D-Link DIR-600L

Overview

A critical security vulnerability, CVE-2025-4348, has been identified in D-Link DIR-600L up to version 2.07B01. This vulnerability has been rated as critical, with a CVSS Severity Score of 8.8, indicating a significant risk to system security. The vulnerability arises from a buffer overflow condition in the function formSetWanL2TP, triggered by the manipulation of the ‘host’ argument. This vulnerability can be exploited remotely, potentially leading to a system compromise or data leakage. Importantly, this vulnerability only affects products that are no longer supported by D-Link, making mitigation more challenging.

Vulnerability Summary

CVE ID: CVE-2025-4348
Severity: Critical (CVSS: 8.8)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System compromise and potential data leakage

Affected Products

Product | Affected Versions

D-Link DIR-600L | Up to 2.07B01

How the Exploit Works

The exploit works by sending a specially crafted request to the formSetWanL2TP function in the D-Link DIR-600L. This function, which handles the ‘host’ argument in the application, does not properly validate or sanitize the input. As a result, an attacker can overflow the buffer by sending an excessively long string in the ‘host’ argument, leading to memory corruption. This can cause the application to crash or potentially allow the execution of arbitrary code.

Conceptual Example Code

Here is a conceptual example of how a malicious HTTP request might look like:

POST /formSetWanL2TP HTTP/1.1
Host: target.example.com
Content-Type: application/json
{ "host": "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA...[continue A's to overflow buffer]... }

In this example, the ‘host’ argument is filled with an excessive number of ‘A’ characters, causing a buffer overflow.

Mitigation

The primary form of mitigation is to apply the vendor patch. However, since the affected product is no longer supported by the vendor, this may not be possible. In such cases, users can use a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) to detect and block attempts to exploit this vulnerability. These systems can be configured to monitor for excessively long ‘host’ arguments and block or alert on such attempts. However, these are temporary mitigation measures, and users are encouraged to upgrade to a supported product as soon as possible.