Executive Summary

This vulnerability is a stack-based buffer overflow found in the Belkin F9K1122 router firmware version 1.00.33. It occurs in the web interface function formCrossBandSwitch, which processes a user-supplied parameter called "webpage." The function copies this parameter into a fixed-size buffer without checking its length, allowing an attacker to overflow the buffer by sending an excessively long "webpage" value via a POST request to the /goform/formCrossBandSwitch endpoint.

Because there is no bounds checking, the overflow can overwrite adjacent memory, potentially leading to denial of service or remote code execution on the device.

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Impact Analysis

Exploiting this vulnerability can allow an attacker to remotely execute arbitrary code or cause a denial of service on the affected Belkin F9K1122 router. This means the attacker could take control of the device, disrupt its normal operation, or use it as a foothold to launch further attacks within the network.

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Detection Guidance

This vulnerability can be detected by monitoring for POST requests sent to the /goform/formCrossBandSwitch endpoint containing an excessively long "webpage" parameter. Such requests may indicate attempts to exploit the stack-based buffer overflow.

A practical detection method is to capture and analyze HTTP traffic targeting the Belkin F9K1122 router, specifically looking for unusually large payloads in the "webpage" parameter within POST requests.

Example commands to detect potential exploitation attempts include using network packet capture tools like tcpdump or tshark:

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

Inspect the captured POST data for the "webpage" parameter and check if its length exceeds normal expected sizes, which could indicate an exploit attempt.

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Mitigation Strategies

Immediate mitigation steps include restricting access to the vulnerable router's web interface to trusted networks only, such as by using firewall rules or network segmentation.

Disabling remote management or remote access to the router's web interface can prevent attackers from launching the exploit remotely.

Monitor network traffic for suspicious POST requests targeting the /goform/formCrossBandSwitch endpoint with large "webpage" parameters and block or alert on such traffic.

Since the vendor has not responded with a patch, consider replacing or upgrading the device firmware if a fixed version becomes available or using alternative hardware until a fix is released.

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Compliance Impact

The provided information does not specify how the vulnerability in Belkin F9K1122 affects compliance with common standards and regulations such as GDPR or HIPAA.

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