Buffer Overflow in Tenda CH22 Router Firmware

Executive Summary

This vulnerability exists in the Tenda CH22 device, specifically in the function formCertListInfo within the file /goform/CertListInfo. It is caused by improper handling of the argument 'Name', which leads to a buffer overflow condition. This flaw can be exploited remotely, allowing an attacker to potentially execute arbitrary code or cause a denial of service.

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Detection Guidance

Detecting this vulnerability on your network or system involves checking for the presence of the vulnerable Tenda CH22 device and verifying if the specific vulnerable endpoint is exposed. Since the vulnerability is in the function formCertListInfo of the file /goform/CertListInfo, you can look for signs of exploitation or misconfiguration.

• Use network scanning tools like Nmap to identify Tenda CH22 devices on your network. Example command: nmap -p 80,443 --script http-title <network_range> | grep 'Tenda CH22'.
• Check if the vulnerable endpoint /goform/CertListInfo is accessible. You can use curl to send a request: curl -v http://<device_ip>/goform/CertListInfo. If the endpoint responds, the device may be vulnerable.
• Monitor network traffic for unusual requests to the /goform/CertListInfo endpoint, especially those manipulating the 'Name' argument, which could indicate exploitation attempts.

Since the exploit has been made public, ensure your intrusion detection systems (IDS) or web application firewalls (WAF) are updated to detect and block known attack patterns targeting this vulnerability.

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Impact Analysis

Exploitation of this vulnerability can lead to severe impacts including remote code execution or denial of service on the affected device. Because the attack can be launched remotely without user interaction, it poses a significant security risk. The high CVSS scores (up to 9.0 in version 2.0) reflect the critical nature of this vulnerability.

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Compliance Impact

This vulnerability, a buffer overflow in Tenda CH22 1.0.0.1, can have significant implications for compliance with standards and regulations like GDPR and HIPAA.

• GDPR: The vulnerability allows remote exploitation, potentially leading to unauthorized access or disclosure of personal data. Under GDPR, organizations must implement appropriate security measures to protect personal data. A buffer overflow exploit that compromises confidentiality (C:H) and integrity (I:H) could result in a data breach, triggering GDPR's breach notification requirements and potential fines for non-compliance.
• HIPAA: For organizations handling protected health information (PHI), this vulnerability could lead to unauthorized access or modification of sensitive data. HIPAA requires safeguards to ensure the confidentiality, integrity, and availability of PHI. A successful exploit could violate these requirements, leading to penalties under the HIPAA Security Rule.

The CVSS v3.1 score of 8.8 (High) and v2.0 score of 9.0 (High) indicate a severe risk, which may require immediate remediation to maintain compliance with these regulations.

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Mitigation Strategies

To mitigate this vulnerability, follow these immediate steps to reduce the risk of exploitation.

• Isolate or disconnect the vulnerable Tenda CH22 device from the network until a patch or firmware update is applied. This prevents remote exploitation.
• If the device must remain online, restrict access to it by implementing network-level controls such as firewalls or VLANs. Allow only trusted IP addresses to communicate with the device.
• Check the Tenda official website (https://www.tenda.com.cn) for firmware updates or patches that address this vulnerability. Apply the update as soon as it becomes available.
• Monitor the device for any suspicious activity, such as unexpected requests to the /goform/CertListInfo endpoint or unusual outbound connections.
• If no patch is available, consider replacing the device with a non-vulnerable model or one that receives regular security updates.

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