Stack Overflow in Tenda O3 Wireless Router

Executive Summary

CVE-2026-36784 is a stack-based buffer overflow vulnerability found in the Tenda O3 Wireless Router version 1.0.0.5. It occurs in the fromNetToolGet CGI handler when a crafted HTTP request is sent with an excessively long 'ip' parameter.

The vulnerability arises because the 'ip' parameter is retrieved using a function that does not check the length and then copied into a fixed-size buffer using strcpy, which does not perform bounds checking. If the 'ip' parameter is longer than the buffer, it overwrites adjacent memory on the stack.

This memory overwrite can cause the router process to crash or become unstable, leading to a denial of service (DoS) condition.

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Impact Analysis

This vulnerability can impact you by allowing an attacker to cause a denial of service (DoS) on your Tenda O3 Wireless Router.

By sending a specially crafted HTTP request with a maliciously long 'ip' parameter, an attacker can crash the router's process or cause device instability, potentially disrupting your network connectivity.

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Detection Guidance

This vulnerability can be detected by monitoring for HTTP requests sent to the `fromNetToolGet` endpoint containing an unusually long or malformed `ip` parameter.

A practical detection method is to capture and analyze HTTP traffic targeting the Tenda O3 router, specifically looking for requests to the `fromNetToolGet` CGI handler with an `ip` parameter that exceeds normal length.

For example, using command-line tools like curl or wget, you can simulate or detect suspicious requests:

• curl -v 'http://<router-ip>/fromNetToolGet?ip=<very_long_string>'
• tcpdump or Wireshark filters to capture HTTP requests to `/fromNetToolGet` endpoint and inspect the `ip` parameter length.

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Mitigation Strategies

Immediate mitigation steps include avoiding sending or allowing HTTP requests with excessively long `ip` parameters to the `fromNetToolGet` endpoint on the affected Tenda O3 router version v1.0.0.5.

If possible, restrict access to the router's management interface to trusted networks or IP addresses to reduce exposure.

Monitor the router for crashes or instability that may indicate exploitation attempts.

Contact the vendor for firmware updates or patches that address this stack overflow vulnerability.

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Compliance Impact

The provided information does not specify any direct impact of the vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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