Stack-Based Buffer Overflow in Tenda BE12 Pro

Executive Summary

CVE-2026-15692 is a stack-based buffer overflow vulnerability in the Tenda BE12 Pro router, specifically in firmware version 16.03.66.23. The issue resides in the `fromSafeUrlFilter` function of the `/goform/SafeUrlFilter` endpoint.

The vulnerability occurs because the function uses the unsafe `sprintf` function to copy user-controlled input from the `page` parameter into a fixed-size 256-byte buffer without validating the input length. When the input exceeds this size, it overflows the buffer, corrupting adjacent memory.

This can lead to memory corruption, application crashes, or arbitrary code execution. The attack can be performed remotely, and no authentication is required, making it highly exploitable.

• Affected component: `/goform/SafeUrlFilter` endpoint in Tenda BE12 Pro firmware V16.03.66.23.
• Root cause: Use of `sprintf` without input length validation for the `page` parameter.
• Potential impact: Denial of Service (DoS), arbitrary code execution, or information leakage.

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Impact Analysis

If you are using the Tenda BE12 Pro router with firmware version 16.03.66.23, this vulnerability could have severe consequences for your network and devices.

• An attacker could exploit this vulnerability to gain full control over your router. This includes the ability to execute arbitrary code, which may allow them to install malware or backdoors.
• The attacker could monitor or intercept your network traffic, leading to potential data theft, including sensitive information like passwords, financial details, or personal communications.
• The router could be used as a pivot point to launch attacks against other devices on your network, such as computers, smartphones, or IoT devices.
• A successful exploit could cause the router to crash, resulting in a Denial of Service (DoS) and disrupting your internet connectivity.
• If the attacker executes arbitrary code, they could modify router settings, redirect traffic to malicious sites, or use the router as part of a botnet for larger-scale attacks.

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Compliance Impact

This vulnerability can have significant implications for compliance with various standards and regulations, depending on the context in which the affected router is used.

• GDPR (General Data Protection Regulation): If the router is used in an environment where personal data of EU citizens is processed, this vulnerability could lead to unauthorized access or exposure of that data. Under GDPR, organizations must implement appropriate technical measures to protect personal data. Failure to address this vulnerability could result in non-compliance, leading to fines or legal action if a breach occurs.
• HIPAA (Health Insurance Portability and Accountability Act): In healthcare settings, if the router is part of a network handling protected health information (PHI), this vulnerability could compromise the confidentiality and integrity of PHI. HIPAA requires covered entities to protect PHI from unauthorized access. Exploitation of this vulnerability could result in a breach, triggering reporting obligations and potential penalties.
• PCI DSS (Payment Card Industry Data Security Standard): If the router is used in a network processing payment card data, this vulnerability could expose cardholder data to attackers. PCI DSS mandates strict security controls to protect such data. Non-compliance due to this vulnerability could lead to fines, increased transaction fees, or loss of ability to process payments.
• ISO 27001: Organizations certified under ISO 27001 must maintain an Information Security Management System (ISMS) that includes risk management. This vulnerability represents a significant risk that would need to be addressed to maintain compliance. Failure to mitigate it could result in loss of certification.
• NIST Cybersecurity Framework: Organizations following the NIST framework are required to identify, protect, detect, respond to, and recover from cybersecurity threats. This vulnerability would fall under the 'Protect' function, and failure to address it could hinder compliance with the framework.

In summary, the vulnerability undermines the security controls required by these standards and regulations, potentially leading to non-compliance, legal consequences, and reputational damage.

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Detection Guidance

To detect the CVE-2026-15692 vulnerability on your network or system, you can check if your Tenda BE12 Pro router is running the affected firmware version (16.03.66.23).

• Verify the firmware version by accessing the router's web interface or using commands like 'curl' or 'wget' to fetch the version information from the router's admin page.
• Use network scanning tools like Nmap to identify devices running Tenda BE12 Pro routers. Example command: 'nmap -p 80,443 --open <network_range> -oG - | grep Tenda'.
• Check for unusual traffic or exploitation attempts targeting the '/goform/SafeUrlFilter' endpoint. Tools like Wireshark or tcpdump can be used to monitor HTTP POST requests to this endpoint. Example command: 'tcpdump -i <interface> -s 0 -A 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)' | grep 'SafeUrlFilter'.
• Test for the vulnerability by sending a crafted POST request with an oversized 'page' parameter to the '/goform/SafeUrlFilter' endpoint. If the router crashes or behaves abnormally, it may be vulnerable. Example Python script snippet: 'import requests; requests.post('http://<router_ip>/goform/SafeUrlFilter', data={'page': 'A'*300})'.

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Mitigation Strategies

Immediate steps to mitigate CVE-2026-15692 include the following actions:

• Apply the latest firmware update from Tenda if available. Check the official Tenda website for patches or security advisories.
• Restrict access to the router's admin interface by disabling remote management and ensuring it is only accessible from trusted internal networks.
• Implement network-level protections such as firewalls or intrusion prevention systems (IPS) to block malicious requests targeting the '/goform/SafeUrlFilter' endpoint.
• Replace the unsafe 'sprintf' function with safer alternatives like 'snprintf' in the router's firmware code if you have access to custom firmware or development tools.
• Implement strict input length checks and validate/sanitize all user-provided input to the 'page' parameter in the 'fromSafeUrlFilter' function.
• Adopt the principle of least privilege by ensuring the router's processes run with minimal permissions necessary.
• Monitor the router for signs of exploitation, such as unexpected reboots or unusual network traffic patterns.

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