Executive Summary

[{'type': 'paragraph', 'content': 'CVE-2026-4041 is a stack-based buffer overflow vulnerability found in the Tenda i12 router running firmware version 1.0.0.6(2204).'}, {'type': 'paragraph', 'content': 'The flaw exists in the function vos_strcpy within the /goform/exeCommand file, which processes a user-supplied parameter named "cmdinput."'}, {'type': 'paragraph', 'content': 'Because the vos_strcpy function does not check the length of the input, an attacker can send a specially crafted request with an excessively long "cmdinput" parameter, causing a stack-based buffer overflow.'}, {'type': 'paragraph', 'content': 'This overflow can lead to denial of service (DoS) or potentially allow remote code execution (RCE) on the device.'}] [1, 2, 3]

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Impact Analysis

This vulnerability can be exploited remotely without authentication, making it highly severe.

An attacker can cause denial of service (DoS), disrupting the availability of the device.

More critically, the attacker may execute arbitrary code remotely, compromising the confidentiality, integrity, and availability of the affected router.

Since the exploit is publicly available, the risk of attacks is increased.

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Compliance Impact

I don't know

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Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability can be detected by monitoring for suspicious HTTP POST requests sent to the /goform/exeCommand endpoint containing an excessively long or malformed "cmdinput" parameter. Such requests may indicate attempts to exploit the stack-based buffer overflow.'}, {'type': 'paragraph', 'content': 'A practical detection method is to capture and analyze network traffic for POST requests targeting /goform/exeCommand with unusually large payloads in the cmdinput field.'}, {'type': 'paragraph', 'content': 'Example commands to detect such attempts include using tools like tcpdump or tshark to filter HTTP POST requests to the vulnerable endpoint:'}, {'type': 'list_item', 'content': "tcpdump -A -s 0 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)' | grep '/goform/exeCommand'"}, {'type': 'list_item', 'content': 'tshark -Y \'http.request.method == "POST" and http.request.uri contains "/goform/exeCommand"\' -T fields -e http.file_data'}, {'type': 'paragraph', 'content': 'Inspect the captured payloads for abnormally long or repetitive characters in the cmdinput parameter, which may indicate exploitation attempts.'}] [3]

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Mitigation Strategies

There are no known official patches or vendor fixes available for this vulnerability in the Tenda i12 firmware version 1.0.0.6(2204).

Immediate mitigation steps include:

• Restrict or block remote access to the /goform/exeCommand endpoint on the affected device using firewall rules or network segmentation.
• Disable remote management features on the router if possible to reduce exposure.
• Monitor network traffic for exploitation attempts and respond accordingly.

Ultimately, it is recommended to replace the affected Tenda i12 device with a secure alternative, as the vulnerability allows remote code execution and denial of service without authentication.

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