Executive Summary

This vulnerability exists in Tenda HG7HG9 and HG10 devices, specifically in the function formPPPEdit within the file /boaform/formPPPEdit. It is caused by improper handling of the argument encodename, which leads to a stack-based buffer overflow.

An attacker can exploit this vulnerability remotely by manipulating the encodename argument, potentially causing the device to behave unexpectedly or allowing the attacker to execute arbitrary code.

The exploit for this vulnerability has been made public.

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Impact Analysis

This vulnerability can have serious impacts including remote code execution due to the stack-based buffer overflow, which can allow an attacker to take control of the affected device.

Because the attack can be launched remotely without user interaction, it increases the risk of unauthorized access, data compromise, or disruption of device functionality.

The high CVSS scores (up to 9.0 in version 2.0) indicate a critical severity level, meaning the vulnerability could lead to significant confidentiality, integrity, and availability impacts.

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Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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Detection Guidance

This vulnerability can be detected by monitoring for unusual POST requests to the endpoint /boaform/formPPPEdit with an abnormally long encodename parameter.

A practical detection method is to capture and analyze HTTP traffic to identify such suspicious requests targeting the vulnerable Tenda devices.

For example, using a network packet capture tool like tcpdump or Wireshark, you can filter HTTP POST requests to /boaform/formPPPEdit and check the length of the encodename parameter.

• tcpdump -i <interface> -A -s 0 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)'
• Use grep or similar tools on captured traffic to find POST requests containing /boaform/formPPPEdit and inspect the encodename parameter length.

Additionally, monitoring the Boa web server process for crashes or restarts may indicate exploitation attempts.

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Mitigation Strategies

Immediate mitigation steps include restricting access to the vulnerable web management interface to trusted networks only.

Disabling remote management or blocking HTTP POST requests to /boaform/formPPPEdit at the network perimeter can prevent exploitation.

Monitoring and limiting the length of parameters sent to the web interface, especially the encodename parameter, can reduce risk.

If possible, update the device firmware to a version where this vulnerability is patched.

In the absence of a patch, consider isolating the device from untrusted networks and applying strict firewall rules.

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