Command Injection in Comfast CF-WR631AX Router

Executive Summary

This vulnerability is a flaw found in the Comfast CF-WR631AX V3 device firmware up to version 2.7.0.8. It affects the system function in the API endpoint located at /cgi-bin/mbox-config?section=ping_config. Specifically, the vulnerability arises from improper handling of the 'destination' argument, which allows an attacker to perform OS command injection.

This means that an attacker can remotely send crafted input to this endpoint to execute arbitrary operating system commands on the device.

The exploit for this vulnerability has been published, making it possible for attackers to use it in real-world attacks. The vendor was informed but did not respond.

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Impact Analysis

This vulnerability can have serious impacts because it allows remote attackers to execute arbitrary operating system commands on the affected device.

• Unauthorized control over the device, potentially leading to device compromise.
• Disruption of device functionality or network services.
• Potential pivot point for further attacks within the network.
• Exposure of sensitive information or data breaches if the device is used to handle such data.

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Compliance Impact

The provided information does not specify how this vulnerability impacts compliance with common standards and regulations such as GDPR or HIPAA.

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Detection Guidance

This vulnerability can be detected by testing the /cgi-bin/mbox-config?section=ping_config API endpoint for command injection via the destination parameter.

One method is to send a crafted JSON payload to the endpoint with the destination parameter containing a command injection payload, such as: 127.0.0.1"; id; #

If the response returns output from the injected command (e.g., the output of the 'id' command), it indicates the vulnerability is present.

Example command using curl to test the vulnerability:

• curl -X POST http://[router-ip]/cgi-bin/mbox-config?section=ping_config -d '{"method":"SET","section":"ping_config","destination":"127.0.0.1"; id; #"}' -H 'Content-Type: application/json'

A successful injection will execute the 'id' command on the router and return its output.

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Mitigation Strategies

Immediate mitigation steps include:

• Restrict remote access to the vulnerable API endpoint by limiting network exposure or firewalling access to trusted hosts only.
• Disable or block access to the /cgi-bin/mbox-config?section=ping_config endpoint if possible.
• Monitor network traffic for suspicious requests containing command injection patterns, such as semicolons or shell commands in the destination parameter.
• If available, update the firmware to a version that patches this vulnerability. However, the vendor has not responded to this disclosure, so an official patch may not be available.
• Consider isolating the affected device from critical networks until a fix is applied.

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