CVE-2025-5855: Critical Remote Buffer Overflow Vulnerability in Tenda AC6 15.03.05.16

Overview

The cybersecurity landscape is always evolving, and vulnerabilities can pop up in even the most unexpected places. One such vulnerability, identified as CVE-2025-5855, has been discovered in the Tenda AC6 15.03.05.16. This critical vulnerability, which pertains to the function formSetRebootTimer of the file /goform/SetRebootTimer, can potentially lead to a system compromise or even data leakage. Given the severity of the exploit and its ability to be initiated remotely, it’s crucial that users understand the vulnerability and take appropriate steps to mitigate its effects.

Vulnerability Summary

CVE ID: CVE-2025-5855
Severity: Critical – CVSS 8.8
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System compromise or data leakage

Affected Products

Product | Affected Versions

Tenda AC6 | 15.03.05.16

How the Exploit Works

This vulnerability is a stack-based buffer overflow vulnerability, meaning it involves the overflowing of a memory space called a stack. In this case, the manipulation of the argument rebootTime in the function formSetRebootTimer leads to this overflow. By supplying an excessively long value for rebootTime, an attacker can overflow the buffer, and overwrite adjacent memory locations.
The danger lies in the fact that overwritten memory may contain executable code, which can be replaced with malicious instructions. This can result in a variety of negative outcomes, ranging from program crashes to the execution of arbitrary code, potentially granting the attacker control over the system.

Conceptual Example Code

The following conceptual example illustrates how an attacker might exploit this vulnerability in a HTTP request:

POST /goform/SetRebootTimer HTTP/1.1
Host: target.example.com
Content-Type: application/json
{ "rebootTime": "VeryLongStringToOverflowBuffer..." }

In this example, the string assigned to “rebootTime” is excessively long, intended to overflow the buffer and potentially overwrite important data or executable code. The specifics of the string would depend on the exact nature of the vulnerability and the attacker’s goal.

Countermeasures

The best way to mitigate this vulnerability is to apply the vendor patch. In scenarios where this is not immediately possible, the use of a Web Application Firewall (WAF) or Intrusion Detection System (IDS) could provide temporary mitigation.
It’s important to note that these are only temporary solutions. They may not completely prevent exploitation and may have other adverse effects on system performance or functionality. Therefore, applying the vendor patch as soon as feasible remains the best way to secure systems against the CVE-2025-5855 vulnerability.