Executive Summary

The Tenda AC7 router with firmware version V15.03.06.44 contains a stack buffer overflow vulnerability in the /goform/AdvSetMacMtuWan interface via the mac parameter.

This vulnerability occurs because the strcpy function is used to copy user-controlled input into a stack buffer without checking the size, allowing the input to exceed the buffer's capacity.

Attackers can exploit this by sending a maliciously crafted POST request with an excessively long mac parameter to the vulnerable endpoint, which can trigger the overflow.

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Impact Analysis

Exploitation of this vulnerability can lead to denial-of-service conditions or remote arbitrary code execution on the affected device.

This means an attacker could crash the router or potentially take control of it remotely by sending specially crafted data.

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Detection Guidance

This vulnerability can be detected by monitoring network traffic for POST requests to the /goform/AdvSetMacMtuWan endpoint containing an unusually long or malformed mac parameter.

A practical detection method is to capture and analyze HTTP POST requests targeting this endpoint to identify attempts to exploit the stack buffer overflow.

• Use a network packet capture tool like tcpdump or Wireshark to filter HTTP POST requests to /goform/AdvSetMacMtuWan.
• Example tcpdump command: tcpdump -i <interface> -A 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)' | grep '/goform/AdvSetMacMtuWan'
• Inspect the POST data for the mac parameter and check if its length exceeds normal expected values.

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Mitigation Strategies

Immediate mitigation steps include restricting access to the vulnerable /goform/AdvSetMacMtuWan endpoint to trusted users or networks only.

Additionally, monitoring and blocking suspicious POST requests with excessively long mac parameters can help prevent exploitation.

If possible, update the router firmware to a version where this vulnerability is patched or contact the vendor for a security update.

As a temporary measure, consider disabling remote management features that expose this endpoint.

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