CVE-2026-19792: Tenda G0 Buffer Overflow Vulnerability

Overview

The CVE-2026-19792 vulnerability affects the Tenda G0 device, specifically the httpd web management interface up to version 20260625. This vulnerability is caused by a buffer overflow in the `setPortMapping` function of the `/goform/module` file. The attack can be carried out remotely, and an exploit has been released to the public.

Understanding the Vulnerability / Threat

Root Cause Analysis

The root cause of this vulnerability is a buffer overflow in the `setPortMapping` function. This function is part of the httpd web management interface and is responsible for setting port mappings. The buffer overflow occurs when an attacker manipulates the `portMappingServer`, `portMappingInternal`, or `portMappingExternal` arguments, causing the buffer to overflow. This vulnerability belongs to the CWE-119 and CWE-120 categories, which involve improper handling of memory buffers.

Attack Surface & Vector

The attack surface of this vulnerability is the httpd web management interface of the Tenda G0 device. The attack vector is remote, meaning an attacker can exploit this vulnerability without physical access to the device. The preconditions for exploiting this vulnerability are: - The attacker must be able to send HTTP requests to the device's web management interface. - The device must be running firmware up to version 20260625.

Exploitation Mechanics — Scenario Walkthrough

Scenario: Compromising a Tenda G0 Device via Buffer Overflow 1. Initial Position: The attacker is a remote unauthenticated user with access to the device's web management interface. 2. Triggering the Flaw: The attacker crafts an HTTP request to the `/goform/module` endpoint with a manipulated `portMappingServer`, `portMappingInternal`, or `portMappingExternal` argument. This argument is designed to exceed the buffer size, causing a buffer overflow. 3. What Breaks: The buffer overflow causes the device's httpd service to fail, allowing the attacker to execute arbitrary code or crash the service. 4. Attacker's Prize: The attacker gains remote code execution or the ability to crash the service, potentially leading to a denial-of-service (DoS) condition or further exploitation.

Real-World Impact

The impact of this vulnerability can be significant. An attacker could exploit this vulnerability to: - Execute arbitrary code on the device. - Crash the httpd service, leading to a DoS condition. - Potentially gain access to the device's network and other connected devices.

Detection & Defense

Immediate Mitigations

- Upgrade the Tenda G0 device to a version later than 20260625. - Limit access to the device's web management interface to trusted IP addresses. - Implement a web application firewall (WAF) to detect and block suspicious HTTP requests.

Detection Strategies

- Monitor the device's logs for suspicious HTTP requests to the `/goform/module` endpoint. - Implement a SIEM system to detect and alert on potential buffer overflow attempts.

Long-Term Hardening

- Regularly update and patch the device's firmware. - Implement a defense-in-depth strategy, including network segmentation and access controls. - Conduct regular security audits and vulnerability assessments.

Key Takeaways

- The CVE-2026-19792 vulnerability is a buffer overflow vulnerability in the Tenda G0 device's httpd web management interface. - The vulnerability can be exploited remotely and has a CVSS score of 8.8. - An attacker could exploit this vulnerability to execute arbitrary code or crash the httpd service. - Immediate mitigations include upgrading the device's firmware and limiting access to the web management interface.

Sources

- National Vulnerability Database (NVD) - CVE-2026-19792