Overview
In the ever-evolving world of cybersecurity, vulnerabilities are frequently being discovered and exploited. One such vulnerability, CVE-2025-9392, has been identified in multiple models of Linksys routers. This vulnerability, if exploited, could lead to severe consequences, including system compromise or data leakage. This blog post aims to explain the vulnerability details, how it affects the Linksys routers, and the mitigation steps to guard against potential attacks.
The vulnerability in question targets the function ‘qosClassifier’ of the file ‘/goform/qosClassifier’ in several Linksys routers. This stack-based buffer overflow can be triggered remotely, and the exploit has been publicly disclosed. Despite being informed, the vendor has failed to respond, escalating the risk associated with this vulnerability.
Vulnerability Summary
CVE ID: CVE-2025-9392
Severity: High (8.8 CVSS Score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System compromise or data leakage
Affected Products
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Product | Affected Versions
Linksys RE6250 | 1.0.013.001, 1.0.04.001, 1.0.04.002
Linksys RE6300 | 1.0.013.001, 1.0.04.001, 1.0.04.002
Linksys RE6350 | 1.0.013.001, 1.0.04.001, 1.0.04.002
Linksys RE6500 | 1.0.013.001, 1.0.04.001, 1.0.04.002
Linksys RE7000 | 1.1.05.003
Linksys RE9000 | 1.2.07.001
How the Exploit Works
The exploit works by manipulating the arguments ‘dir/sFromPort/sToPort/dFromPort/dToPort/protocol/layer7/dscp/remark_dscp’ in the ‘qosClassifier’ function of the file ‘/goform/qosClassifier’. This manipulation causes a stack-based buffer overflow. A buffer overflow occurs when more data is put into a buffer than it can hold. In this case, the overflow could lead to a system crash or allow the execution of arbitrary code, potentially compromising the system.
Conceptual Example Code
This conceptual example illustrates how an attacker might exploit this vulnerability:
POST /goform/qosClassifier HTTP/1.1
Host: target.example.com
Content-Type: application/json
{
"dir": "excessive_data",
"sFromPort": "excessive_data",
"sToPort": "excessive_data",
"dFromPort": "excessive_data",
"dToPort": "excessive_data",
"protocol": "excessive_data",
"layer7": "excessive_data",
"dscp": "excessive_data",
"remark_dscp": "excessive_data"
}The ‘excessive_data’ could be a long string of characters designed to overflow the buffer. Successful exploitation could lead to the execution of malicious code with the same privileges as the process being exploited.
As a mitigation measure, it is recommended to apply any available vendor patches or use Web Application Firewall (WAF) or Intrusion Detection System (IDS) as temporary mitigation. Keep in mind that these are temporary solutions until the vendor provides a permanent fix.