Executive Summary

CVE-2026-11504 is a stack-based buffer overflow vulnerability found in the Tenda CX12L router firmware version 16.03.53.12. It occurs in the Wi-Fi Schedule Configuration Endpoint, specifically in the setSchedWifi function of the /goform/openSchedWifi file.

The vulnerability arises because the function processes user-supplied parameters schedStartTime and schedEndTime without proper length validation. It uses unsafe string copy operations (strcpy) to copy these parameters into a fixed-size 25-byte buffer, which can be overflowed by providing oversized input.

This buffer overflow can lead to memory corruption, potentially causing Denial of Service (DoS) or allowing an attacker to execute arbitrary code remotely.

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Impact Analysis

This vulnerability can have serious impacts including remote Denial of Service (DoS), where the router may crash or become unresponsive.

More critically, it may allow an attacker to execute arbitrary code on the device remotely, potentially taking full control of the router.

Such control could be used to intercept network traffic, modify router settings, or launch further attacks on connected devices.

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Detection Guidance

This vulnerability can be detected by monitoring or testing the /goform/openSchedWifi endpoint on Tenda CX12L routers running firmware version 16.03.53.12. Specifically, sending crafted requests with oversized schedStartTime or schedEndTime parameters can reveal if the device is vulnerable to stack-based buffer overflow.

A practical detection method involves sending HTTP POST requests to the /goform/openSchedWifi endpoint with abnormally long schedStartTime or schedEndTime values and observing the device's behavior for crashes or abnormal responses.

• Use curl to send a test request with an oversized schedStartTime parameter, for example: curl -X POST http://<router-ip>/goform/openSchedWifi -d "schedStartTime=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA&schedEndTime=10:00"
• Monitor the router for crashes, reboots, or abnormal behavior after sending such requests.
• Network intrusion detection systems (NIDS) can be configured to alert on unusually long parameters sent to /goform/openSchedWifi.

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Mitigation Strategies

Immediate mitigation steps include avoiding exposure of the vulnerable endpoint to untrusted networks and restricting access to the router's management interface.

If possible, apply firmware updates or patches provided by the vendor that replace unsafe functions like strcpy with safer alternatives and implement input validation.

In the absence of an official patch, consider disabling or restricting access to the Wi-Fi Schedule Configuration feature to prevent exploitation.

Monitor network traffic for suspicious requests targeting /goform/openSchedWifi and block malicious IP addresses.

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Compliance Impact

The vulnerability in Tenda CX12L allows remote attackers to cause a stack-based buffer overflow, potentially leading to memory corruption, Denial of Service (DoS), or arbitrary code execution. Such security weaknesses can compromise the confidentiality, integrity, and availability of data processed or transmitted by the device.

Because this vulnerability can lead to unauthorized access or disruption of services, it may negatively impact compliance with standards and regulations like GDPR and HIPAA, which require protection of personal and sensitive data against unauthorized access and ensuring system availability.

However, the provided information does not explicitly detail the direct impact on compliance frameworks or specific regulatory requirements.

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