Overview
A critical vulnerability, identified as CVE-2025-4496, has been discovered affecting a range of TOTOLINK router models. The vulnerability lies in the CloudACMunualUpdate function of the file /cgi-bin/cstecgi.cgi and can potentially lead to a system compromise or data leakage. This vulnerability has been marked crucial due to its high CVSS Severity Score and its potential for remote exploitation. As the exploit has been publicly disclosed, it poses a significant risk to all users of the affected router models.
Vulnerability Summary
CVE ID: CVE-2025-4496
Severity: Critical (8.8 CVSS Score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System Compromise and Data Leakage
Affected Products
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Product | Affected Versions
TOTOLINK T10 | 4.1.8cu.5241_B20210927
TOTOLINK A3100R| 4.1.8cu.5241_B20210927
TOTOLINK A950RG | 4.1.8cu.5241_B20210927
TOTOLINK A800R | 4.1.8cu.5241_B20210927
TOTOLINK N600R | 4.1.8cu.5241_B20210927
TOTOLINK A3000RU | 4.1.8cu.5241_B20210927
TOTOLINK A810R | 4.1.8cu.5241_B20210927
How the Exploit Works
The vulnerability revolves around the CloudACMunualUpdate function in the /cgi-bin/cstecgi.cgi file. The FileName argument, when manipulated, can lead to a buffer overflow condition. This could potentially allow an attacker to execute arbitrary code on the system or cause the system to crash, leading to a denial of service. The attack can be initiated remotely, without requiring any user interaction or special privileges.
Conceptual Example Code
As a conceptual example, an attacker could exploit this vulnerability by sending a specially crafted HTTP request to the target system. It could look something like this:
POST /cgi-bin/cstecgi.cgi/CloudACMunualUpdate HTTP/1.1
Host: target.example.com
Content-Type: application/json
{ "FileName": "malicious_payload..." }In this example, the “FileName” argument is manipulated with a malicious payload that causes a buffer overflow, leading to the unintended consequences.
Mitigation
Users of the affected TOTOLINK routers are strongly advised to apply the vendor patch as soon as it becomes available. In the meantime, implementing a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) can serve as a temporary mitigation measure to guard against potential attacks exploiting this vulnerability.