Authentication Bypass in Netcore NR256CN Router

Executive Summary

Netcore NR256CN through version 1.5.140116 has an authentication bypass flaw. Unauthenticated attackers can access protected management CGI handlers by adding a public route prefix like l7_web_auth.cgi or an .ico route to the URI. This allows them to invoke sensitive management functions without valid credentials.

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Detection Guidance

Check for unauthenticated access to protected management CGI handlers by testing paths like /l7_web_auth.cgi or .ico routes. Use curl commands to send requests to these paths and verify if they return sensitive data without credentials. Example: curl http://<target-ip>/l7_web_auth.cgi/admin or curl http://<target-ip>/test.ico/admin.

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Impact Analysis

Attackers could exploit this to gain unauthorized access to device management interfaces, modify configurations, or extract sensitive data. Since no authentication is required, the risk of remote compromise is high, potentially leading to full system control or data breaches.

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Compliance Impact

This vulnerability could lead to unauthorized data access or modification, violating confidentiality requirements in GDPR and HIPAA. Organizations using affected devices may face compliance failures, legal penalties, and reputational damage due to potential data breaches.

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Mitigation Strategies

Update the Netcore NR256CN firmware to the latest version that patches this vulnerability. If an update is unavailable, restrict access to management interfaces via network segmentation or firewall rules. Disable public routes that allow unauthenticated access to protected handlers.

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