Stack-Based Buffer Overflow in Tenda JD12L Router

Executive Summary

CVE-2026-13516 is a critical buffer overflow vulnerability in the Tenda Router JD12L Pro firmware version 16.03.53.23. It exists in the function fromSetWifiGusetBasic within the /goform/WifiGuestSet endpoint. The vulnerability arises because the function uses the unsafe strcpy function to copy the "shareSpeed" parameter without proper bounds checking.

An attacker can send an oversized input for the "shareSpeed" parameter, which overwrites stack memory. This can cause application crashes, memory corruption, or allow arbitrary code execution. The attack can be performed remotely and does not require authentication.

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Impact Analysis

This vulnerability can have severe impacts including denial of service by crashing the device, information leakage, or even full device takeover through arbitrary code execution.

• Denial of Service (DoS) by causing application crashes.
• Memory corruption leading to unpredictable device behavior.
• Remote arbitrary code execution allowing an attacker to control the device.
• No authentication is required, increasing the risk of exploitation.

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Detection Guidance

This vulnerability can be detected by monitoring for suspicious POST requests to the `/goform/WifiGuestSet` endpoint containing an unusually large or malformed "shareSpeed" parameter. Such requests may indicate attempts to exploit the stack-based buffer overflow.

A practical detection method is to capture and analyze network traffic targeting the affected router, specifically looking for POST requests with oversized "shareSpeed" values.

Example command using curl to test the vulnerability by sending a large "shareSpeed" parameter:

• curl -X POST http://[router_ip]/goform/WifiGuestSet -d "shareSpeed=$(python3 -c 'print("A"*1000)')"

Additionally, network intrusion detection systems (NIDS) can be configured to alert on POST requests to `/goform/WifiGuestSet` with unusually large payloads or unexpected parameter sizes.

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Mitigation Strategies

Immediate mitigation steps include restricting access to the vulnerable endpoint by limiting network exposure, such as placing the device behind a firewall or disabling remote management if not needed.

Apply any available firmware updates or patches from the vendor that address this vulnerability.

If patching is not immediately possible, consider implementing network-level protections such as blocking or filtering POST requests to `/goform/WifiGuestSet`.

Follow secure coding and configuration practices, including input validation and least privilege principles, as recommended for long-term remediation.

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Compliance Impact

The provided information does not specify how the CVE-2026-13516 vulnerability impacts compliance with common standards and regulations such as GDPR or HIPAA.

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