External risk intelligence

Tenda W6-S Stack Overflow in WiFi SSID Endpoint.

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-67822

The vulnerability exists in the web management interface of a Tenda W6-S networking device. Such interfaces are commonly exposed on the network and frequently accessed or reachable via the internet as part of the device's role as a network management endpoint.

Buffer Overflow

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A critical vulnerability has been identified in Tenda W6-S networking devices, specifically related to how they handle certain network requests. This flaw could allow unauthorized access and control if exploited. While the immediate business impact is unclear without further analysis, the nature of this vulnerability warrants attention to understand its relevance to our environment.

A network device flaw allows unauthorized control.
It affects a common internet-facing management interface.
Confirm relevance and potential exposure to our environment.

Attack Path

How an attacker could exploit the issue

An attacker can reach the vulnerable component via the network by targeting the device's web management interface. This interface accepts user-controlled data for network settings, which are then processed by a function that fails to check the size of the input. This oversight allows an attacker to send overly large data, causing a stack overflow that can lead to significant system compromise.

Entry requires network access.
Triggered by sending data to a web endpoint.
Risk: full device control and data compromise.

Live Threat

Current exploitation, exposure, and threat context

A stack-based buffer overflow vulnerability in the Tenda W6-S web management interface could allow an unauthenticated attacker to overwrite memory. This could lead to a denial of service or potentially impact the integrity and confidentiality of the device's operations and any data it manages, when the affected endpoint is accessible.

Device configuration and memory could be overwritten.
Network requests can trigger buffer overflow.
Unauthenticated control over device functions.

Operational Fix

Recommended remediation, mitigation, and detection steps

The Tenda W6-S device's web management interface is likely exposed externally, making the platform or infrastructure team responsible for identifying and securing these devices. Initial steps should focus on inventorying all W6-S devices, assessing their network exposure and business criticality, and confirming the accountable owner before planning remediation.

Platform/infrastructure teams own remediation.
Verify device exposure and criticality first.
Plan and coordinate maintenance for fixes.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is the Tenda W6-S device?

The Tenda W6-S is a networking device that provides connectivity management. It includes a built-in web interface that allows administrators to configure network settings, such as wireless SSID parameters, directly through a browser.

What does CVE-2026-67822 mean for this device?

This vulnerability is a stack-based buffer overflow (CWE-121). It occurs when the device's software fails to limit the size of data received through the web interface. Because the system does not check the input length, sending specifically crafted, overly long data can overwrite memory, which may allow an attacker to bypass normal controls and compromise the device.

How is this stack overflow triggered?

The flaw is triggered by sending a malformed request to the '/goform/wifiSSIDset' endpoint on the device. An attacker achieves this by providing excessively large 'GO' or 'index' parameter values. Simply accessing the web interface or navigating normal menus does not trigger the bug; it requires a specific, intentionally oversized input designed to exceed the 64-byte limit of the buffer.

Why is the Tenda W6-S considered exposed?

According to Halo Surface Signal, this device is often used as a network management endpoint, which frequently results in its web management interface being reachable over the network or directly exposed to the internet. Because the interface is designed to be accessible, any device connected to the same network—or the public internet if configured that way—has a potential path to reach this vulnerable component.

What should I do if I manage Tenda W6-S hardware?

First, create an inventory of all Tenda W6-S devices in your environment to identify where they are deployed. Determine if they are accessible from the network or the internet. Coordinate with the relevant platform or infrastructure teams to assess their business criticality and establish a plan for applying vendor-provided maintenance or updates as they become available.

References

github.com/Tristerjh/Tenda/blob/main/Tenda_W6-S_GO_overflow.md

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.