# CVE-2026-51843: Tenda AC7 stack buffer overflow in AdvSetMacMtuWan

Source: https://junglewise.ai/threats/cve-2026-51843-tenda-ac7-stack-buffer-overflow-in-advsetmacmtuwan  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-19. Updated: 2026-06-21  
License: CC BY 4.0 with a link back

CVE-2026-51843 · Severity: info · CVSS 9.8 · Published 2026-06-19

The Tenda AC7 router, a device used to provide wireless internet access, contains a security flaw in its web management interface. An attacker can exploit this flaw by sending a specially crafted request to the router's settings page. If successful, this could allow the attacker to crash the device or take complete control over it, potentially leading to the interception of network traffic or unauthorized access to the home or office network.

Technologies: [Tenda Ac7](https://junglewise.ai/threats/technologies/ac7). Vendors: [Tenda](https://junglewise.ai/threats/vendors/tenda).

## Quick answers

**Is CVE-2026-51843 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-51843 being exploited in the wild.

**How severe is CVE-2026-51843?** Informational severity, with a CVSS score of 9.8, published 19 June 2026.

**Which products and versions are affected?** Tenda Ac7 v15.03.06.44.

**Is there a fix for CVE-2026-51843?** 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-2026-51843 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-51843?** Check whether you run Tenda Ac7 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 Tenda AC7 router firmware version v15.03.06.44. The vulnerability is located within the 'check_param_changed' function, which processes the 'wanMTU' parameter from the '/goform/AdvSetMacMtuWan' interface. The root cause is the use of the unsafe 'strcpy' function to copy user-supplied input into a fixed-size stack buffer without length validation. A remote attacker can exploit this by sending a crafted POST request with an overly long 'wanMTU' string, leading to arbitrary code execution or a denial-of-service (DoS) condition. Based on the PoC, authentication may be required (indicated by a password cookie), but the impact remains critical.

## Affected products

- Tenda AC7 v15.03.06.44

## Timeline

- 2026-04-30: disclosed: Initial discovery and PoC published by KDEV
- 2026-06-19: advisory: CVE published by NVD/MITRE

## References

- [https://www.kdev.site/cve-request_008/](https://www.kdev.site/cve-request_008/)

## Related threats

- [Tenda AC7 stack overflow in /goform/AdvSetMacMtuWan](https://junglewise.ai/threats/cve-2026-51846-tenda-ac7-stack-overflow-in-goform-advsetmacmtuwan)
- [Tenda AC7 stack buffer overflow in AdvSetMacMtuWan](https://junglewise.ai/threats/cve-2026-51845-tenda-ac7-stack-buffer-overflow-in-advsetmacmtuwan)
- [Tenda AC7 stack buffer overflow in AdvSetMacMtuWan](https://junglewise.ai/threats/cve-2026-51844-tenda-ac7-stack-buffer-overflow-in-advsetmacmtuwan)
- [A flaw has been found in Tenda AC7 15.03.06.44. Affected by this issue is the function fromSetSysTime of the file…](https://junglewise.ai/threats/cve-2026-4974-a-flaw-has-been-found-in-tenda-ac7-15-03-06-44-affected-by-this)
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