Overview
A critical vulnerability has been identified in TOTOLINK T10 4.1.8cu.5207, a widely-used software component, which could lead to severe security breaches including system compromise and data leakage if exploited. This vulnerability, classified as CVE-2025-5901, has a significant impact on the security of the systems running the vulnerable versions of the software. Due to the potential severity of this issue and the fact that the exploit has been publicly disclosed, it is of utmost importance that users, administrators and organisations take immediate measures to mitigate any potential risk.
Vulnerability Summary
CVE ID: CVE-2025-5901
Severity: Critical (8.8 CVSS 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 T10 | 4.1.8cu.5207
How the Exploit Works
The vulnerability resides in the Post Request Handler of the file /cgi-bin/cstecgi.cgi. Specifically, it affects the UploadCustomModule function. An attacker can manipulate the File argument leading to a buffer overflow. Buffer overflow is a common type of security flaw where an application writes more data to a block of memory, or buffer, than it was intended to hold. In this case, an attacker can exploit this vulnerability remotely without requiring any user interaction or special privileges.
Conceptual Example Code
Here’s a conceptual example of how the vulnerability might be exploited:
POST /cgi-bin/cstecgi.cgi HTTP/1.1
Host: target.example.com
Content-Type: application/octet-stream
{ "File": "OVERFLOW_BUFFER_WITH_MALICIOUS_CODE" }In this example, the “File” argument is manipulated with a payload that causes the buffer to overflow, potentially allowing an attacker to execute arbitrary code or cause a denial of service.
Mitigation
To protect against this vulnerability, users and administrators are advised to apply the vendor-supplied patch for TOTOLINK T10 4.1.8cu.5207. If a patch cannot be applied immediately, using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can serve as temporary mitigation. In addition, organizations are encouraged to follow best security practices such as limiting access to critical systems and regularly updating and patching all systems.