Executive Summary

CVE-2026-10191 is a buffer overflow vulnerability found in the cgiWifiMacFilterSet function of the Tenda W12 device firmware. It occurs because the software does not properly check the length of the MAC address filter list input, allowing an attacker to send an excessively long MAC address string that overflows the allocated buffer.

This overflow can overwrite critical memory areas, potentially enabling arbitrary code execution, denial of service, or unauthorized access to the device. The vulnerability can be exploited remotely without authentication by sending a specially crafted request to the web interface managing Wi-Fi MAC filtering.

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Impact Analysis

This vulnerability can have serious impacts including allowing attackers to execute arbitrary code on the affected device, causing denial of service, or gaining unauthorized access to network configurations.

• Remote exploitation without authentication makes it easier for attackers to compromise the device.
• Compromise of the device could lead to network disruptions or further attacks on connected systems.
• Attackers could manipulate Wi-Fi MAC filtering settings, potentially bypassing network access controls.

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Detection Guidance

This vulnerability can be detected by monitoring for suspicious HTTP requests targeting the cgiWifiMacFilterSet endpoint on the affected Tenda W12 device. Specifically, look for unusually long or malformed MAC address filter settings in requests to this CGI script, which may indicate attempts to exploit the buffer overflow.

Network detection can involve capturing HTTP traffic and filtering for requests to the /cgiWifiMacFilterSet_overflow endpoint or similar paths related to Wi-Fi MAC filtering configuration.

Example commands to detect potential exploitation attempts include using tools like tcpdump or tshark to capture and filter HTTP requests:

• tcpdump -i <interface> -A -s 0 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)' | grep -i 'cgiWifiMacFilterSet'
• tshark -i <interface> -Y 'http.request.uri contains "cgiWifiMacFilterSet"' -T fields -e http.request.uri

Additionally, inspecting device logs for unusual activity or crashes related to the /bin/httpd process may help identify exploitation attempts.

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Mitigation Strategies

Immediate mitigation steps include restricting access to the vulnerable web interface, especially the cgiWifiMacFilterSet endpoint, by implementing network-level controls such as firewall rules or access control lists to limit who can send requests to the device.

If possible, disable the Wi-Fi MAC filtering feature or the web interface temporarily until a patch or firmware update is available from the vendor.

Monitor the device for unusual behavior or signs of compromise, and consider isolating affected devices from critical network segments.

Apply any available firmware updates or patches provided by Tenda addressing this vulnerability as soon as they are released.

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Compliance Impact

The vulnerability allows remote attackers to execute arbitrary code, cause denial of service, or gain unauthorized access to the affected system by exploiting a stack-based buffer overflow in the Wi-Fi MAC filter configuration interface.

Such unauthorized access and potential control over network device configurations could lead to breaches of confidentiality, integrity, and availability of data, which are critical concerns under standards like GDPR and HIPAA.

Therefore, this vulnerability could negatively impact compliance with these regulations by exposing sensitive personal or health information to unauthorized parties or disrupting the secure operation of network devices.

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