# CVE-2026-36777: Tenda W3 Wireless Router stack overflow in formSetCfm

Source: https://junglewise.ai/threats/cve-2026-36777-tenda-w3-wireless-router-stack-overflow-in-formsetcfm  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-09. Updated: 2026-06-09  
License: CC BY 4.0 with a link back

CVE-2026-36777 · Severity: info · CVSS 7.5 · Published 2026-06-09

The Tenda W3 wireless router, used for home and small office networking, contains a security flaw in its web management interface. By sending a specially crafted web request, an attacker can crash the router, causing it to reboot or become unresponsive. This results in a loss of internet connectivity for all connected users and may require a manual restart to restore service.

Technologies: [Tenda W3 Wireless Router](https://junglewise.ai/threats/technologies/w3-wireless-router). Vendors: [Tenda](https://junglewise.ai/threats/vendors/tenda).

## Quick answers

**Is CVE-2026-36777 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-36777 being exploited in the wild.

**How severe is CVE-2026-36777?** Informational severity, with a CVSS score of 7.5, published 9 June 2026.

**Which products and versions are affected?** Tenda W3 Wireless Router v1.0.0.3(2204).

**Is there a fix for CVE-2026-36777?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-36777 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-36777?** Check whether you run Tenda W3 Wireless Router at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A stack-based buffer overflow exists in the 'formSetCfm' CGI handler of the Tenda W3 router. The vulnerability is located within the 'save_list_data' function, which is called when the 'funcname' parameter is set to 'save_list_data'. The root cause is an unsafe 'sprintf' call (sprintf(acStack_154, "%s.listnum", param_1)) that processes the user-controlled 'funcpara1' parameter without length validation. An unauthenticated remote attacker can exploit this by sending a crafted HTTP request to the 'setcfm' endpoint, leading to a crash of the web service or the entire device (Denial of Service). While primarily a DoS risk, stack overflows of this nature may potentially allow for arbitrary code execution.

## Affected products

- Tenda (Shenzhen Tenda Technology Co., Ltd) W3 Wireless Router v1.0.0.3(2204)

## Timeline

- 2026-03-10: other: CVE request submitted to MITRE
- 2026-06-06: disclosed: Public disclosure via GitHub repository
- 2026-06-09: advisory: NVD published date

## References

- [https://github.com/xhh0124/SemVulLLM/tree/main/W3/formSetCfm](https://github.com/xhh0124/SemVulLLM/tree/main/W3/formSetCfm)

## Related threats

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- [Tenda W3 Wireless Router stack overflow in formwrlSSIDset](https://junglewise.ai/threats/cve-2026-36793-tenda-w3-wireless-router-stack-overflow-in-formwrlssidset)
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- [Tenda W3 Wireless Router stack overflow in formwrlSSIDset](https://junglewise.ai/threats/cve-2026-36771-tenda-w3-wireless-router-stack-overflow-in-formwrlssidset)