CVE-2026-6200: Tenda F456 Buffer Overflow Vulnerability

CVE-2026-6200 Overview

CVE-2026-6200 is a stack-based buffer overflow vulnerability in the Tenda F456 router running firmware version 1.0.0.5. The flaw resides in the formwebtypelibrary function handling requests to the /goform/webtypelibrary endpoint. Attackers can trigger memory corruption by manipulating the menufacturer or Go arguments. The vulnerability is exploitable remotely over the network and requires only low-privileged access. A public exploit has been disclosed, increasing the risk of opportunistic attacks against exposed devices. The weakness is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer).

Critical Impact
Remote attackers with low privileges can corrupt stack memory in the Tenda F456 web management interface, potentially leading to arbitrary code execution or denial of service on the affected router.

Affected Products

Tenda F456 router
Firmware version 1.0.0.5
The formwebtypelibrary handler in /goform/webtypelibrary

Discovery Timeline

2026-04-13 - CVE-2026-6200 published to NVD
2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-6200

Vulnerability Analysis

The vulnerability exists in the formwebtypelibrary function, which processes HTTP requests sent to the /goform/webtypelibrary endpoint of the Tenda F456 web management interface. The function copies attacker-controlled values from the menufacturer and Go parameters into fixed-size stack buffers without validating input length. Sending an oversized string overflows the buffer and overwrites adjacent stack memory, including saved return addresses on the MIPS-based platform typical for Tenda devices.

Successful exploitation can corrupt control flow and lead to arbitrary code execution within the router's web server process, which typically runs with elevated privileges. The disclosure indicates that a public proof of concept exists, lowering the barrier for attackers to weaponize the flaw.

Root Cause

The root cause is the absence of length validation before copying user-supplied input into a stack-allocated buffer. This is a classic instance of [CWE-119], where the bounds of the destination buffer are not enforced. The handler trusts request parameters supplied through the administrative web interface and passes them directly to unsafe string-handling routines.

Attack Vector

The attack vector is network-based. An attacker with low-privileged access to the management interface can send a crafted HTTP request to /goform/webtypelibrary with overly long menufacturer or Go parameters. No user interaction is required. Devices exposing the web interface to untrusted networks face heightened exposure. See the GitHub vulnerability documentation and the VulDB report for additional technical context.

No verified exploit code is reproduced here. Review the referenced advisories for the disclosed proof of concept.

Detection Methods for CVE-2026-6200

Indicators of Compromise

HTTP POST or GET requests to /goform/webtypelibrary containing abnormally long values for the menufacturer or Go parameters.
Unexpected reboots, crashes, or web service unavailability on Tenda F456 devices.
New or unauthorized administrative sessions originating from external addresses to the router management interface.

Detection Strategies

Inspect web access logs and network traffic for requests targeting /goform/webtypelibrary with parameter values exceeding normal lengths.
Deploy network intrusion detection signatures that flag oversized parameter content in HTTP traffic destined for Tenda management endpoints.
Correlate router crash or reboot events with preceding inbound HTTP traffic to the administrative interface.

Monitoring Recommendations

Forward router syslog and web interface logs to a centralized log platform for anomaly analysis.
Alert on any administrative access to the Tenda F456 interface from outside trusted management ranges.
Track outbound connections from the router to unknown hosts, which may indicate post-exploitation command-and-control activity.

How to Mitigate CVE-2026-6200

Immediate Actions Required

Restrict access to the router's web management interface to trusted internal networks only and disable WAN-side management.
Enforce strong, unique administrative credentials and rotate them following any suspected exposure.
Isolate Tenda F456 devices on a dedicated management VLAN until a firmware update is available.

Patch Information

At the time of publication, the vendor has not released a confirmed security patch for CVE-2026-6200. Monitor the Tenda official website for firmware updates addressing firmware version 1.0.0.5 and apply them as soon as they become available.

Workarounds

Disable remote administration on the WAN interface and restrict LAN-side management to designated IP addresses.
Place vulnerable routers behind an upstream firewall that filters HTTP traffic to /goform/webtypelibrary from untrusted sources.
Replace end-of-life or unpatched devices with supported hardware where vendor remediation is not forthcoming.

bash

# Example: block external access to the Tenda management interface using an upstream firewall
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -m iprange ! --src-range 10.0.0.0-10.0.0.255 -j DROP
iptables -A FORWARD -p tcp -d <router_ip> --dport 443 -m iprange ! --src-range 10.0.0.0-10.0.0.255 -j DROP