Executive Summary

CVE-2026-3727 is a stack-based buffer overflow vulnerability found in the Tenda F453 router, version 1.0.0.3. It occurs in the HTTP daemon component, specifically in the function sub_3C6C0 within the file /goform/QuickIndex. The vulnerability is triggered by manipulating the user-supplied parameters mit_linktype and PPPOEPassword. When mit_linktype equals 2, the input is passed to the vulnerable function without any length validation, causing a stack buffer overflow.

This overflow can be exploited remotely by sending crafted HTTP POST requests to the affected endpoint, potentially allowing an attacker to cause a denial of service or execute arbitrary code on the device.

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Impact Analysis

Exploitation of this vulnerability can lead to serious impacts including denial of service (DoS) and remote code execution on the affected Tenda F453 router. This means an attacker could crash the device or take control of it remotely without requiring authentication or physical access.

Such control could compromise the confidentiality, integrity, and availability of the device and the network it supports, potentially allowing attackers to intercept data, disrupt network services, or use the device as a foothold for further attacks.

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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/QuickIndex endpoint, especially those containing the parameter mit_linktype=2 and an unusually long PPPOEPassword value. Such crafted 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/QuickIndex with mit_linktype=2 and large PPPOEPassword parameters.'}, {'type': 'list_item', 'content': 'Use tcpdump or Wireshark to capture HTTP POST requests to /goform/QuickIndex:'}, {'type': 'list_item', 'content': "tcpdump -i <interface> -A 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)' | grep '/goform/QuickIndex'"}, {'type': 'list_item', 'content': 'Use curl or similar tools to test the endpoint by sending a crafted POST request with mit_linktype=2 and a long PPPOEPassword parameter to see if the device responds abnormally or crashes.'}, {'type': 'list_item', 'content': 'Example curl command to test the vulnerability (for controlled testing only):'}, {'type': 'list_item', 'content': 'curl -X POST http://<target-ip>/goform/QuickIndex -d \'mit_linktype=2&PPPOEPassword=$(python3 -c "print(\'A\'*1000)")\''}] [1, 2, 3]

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Mitigation Strategies

There are no known mitigations or countermeasures identified for this vulnerability in the affected Tenda F453 router version 1.0.0.3.

The recommended immediate step is to replace the affected product with an alternative device or firmware version that is not vulnerable.

Additionally, as a temporary measure, you may consider restricting access to the /goform/QuickIndex endpoint by implementing network-level controls such as firewall rules to block incoming HTTP POST requests to this path from untrusted sources.

Monitoring network traffic for exploit attempts and isolating vulnerable devices from untrusted networks can also reduce risk until replacement or patching is possible.

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