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CVE-2025-8136: Buffer Overflow Vulnerability in TOTOLINK A702R

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Overview

CVE-2025-8136 is a critical vulnerability discovered in TOTOLINK A702R 4.0.0-B20230721.1521. This vulnerability is particularly concerning as it affects the HTTP POST Request Handler, one of the most critical components of a web server. More specifically, the issue arises in an undisclosed function of the file /boafrm/formFilter. The vulnerability can be exploited remotely, meaning that an attacker does not need physical access to the device to compromise it. Therefore, it is essential for organizations using TOTOLINK A702R to address this issue promptly to prevent potential system compromise or data leakage.

Vulnerability Summary

CVE ID: CVE-2025-8136
Severity: Critical (8.8 CVSS Severity Score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System compromise and potential data leakage

Affected Products

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Product | Affected Versions

TOTOLINK A702R | 4.0.0-B20230721.1521

How the Exploit Works

The exploit works by manipulating the ‘ip6addr’ argument within the HTTP POST Request Handler. This manipulation causes a buffer overflow in the system. In computing, a buffer overflow occurs when data written to a buffer exceeds its storage capacity, causing the extra data to overflow into adjacent memory locations. This overflow can overwrite other data, crash the system, or lead to the execution of malicious code, potentially granting an attacker control over the system.

Conceptual Example Code

Below is a conceptual example of how the vulnerability might be exploited using a malicious HTTP POST request.

POST /boafrm/formFilter HTTP/1.1
Host: target.example.com
Content-Type: application/json
{ "ip6addr": "2001:0db8:85a3:0000:0000:8a2e:0370:7334" + "A"*10000 }

In this example, the ‘ip6addr’ argument is filled with a legitimate IPv6 address, followed by a large number of ‘A’ characters. The excessive ‘A’ characters cause a buffer overflow, potentially allowing an attacker to compromise the system.

Mitigation Measures

Users of TOTOLINK A702R 4.0.0-B20230721.1521 are advised to apply the vendor patch as soon as it becomes available. In the meantime, temporary mitigation strategies could include the use of a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) to monitor network traffic and block any suspicious activity. It’s also advisable to restrict access to the affected device to trusted networks only, until the patch is applied.

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Disclaimer:

The information and code presented in this article are provided for educational and defensive cybersecurity purposes only. Any conceptual or pseudocode examples are simplified representations intended to raise awareness and promote secure development and system configuration practices.

Do not use this information to attempt unauthorized access or exploit vulnerabilities on systems that you do not own or have explicit permission to test.

Ameeba and its authors do not endorse or condone malicious behavior and are not responsible for misuse of the content. Always follow ethical hacking guidelines, responsible disclosure practices, and local laws.

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