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CVE-2026-51934 – Remote Code Execution via Stack Buffer Overflow – Tenda A18 (Firmware v15.13.07.09)

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Summary

CVE-2026-51934 is a critical buffer overflow vulnerability affecting the Tenda A18 wireless router running firmware version 15.13.07.09. The flaw resides in the fromSetCmdlineRun function, which is reachable via an HTTP request handler and does not validate the size of attacker-supplied input before copying it into a fixed-size buffer. Because the vulnerability requires no authentication or user interaction and is exploitable over the network, it carries a CVSS v3.1 base score of 9.8 (Critical).

Technical details

  • Root cause: CWE-120 (Buffer Copy without Checking Size of Input) — the fromSetCmdlineRun handler copies user-supplied request data into a fixed-size buffer without bounds checking.
  • Trigger condition: An attacker sends a crafted HTTP request to the affected endpoint that invokes fromSetCmdlineRun with an oversized parameter value, overflowing the buffer.
  • Attack vector: Network-based; reachable via the device’s web management interface (httpd component) without requiring authentication or user interaction.
  • Impact: Successful exploitation can corrupt adjacent memory and allows a remote, unauthenticated attacker to execute arbitrary code on the device, fully compromising confidentiality, integrity, and availability.

Affected software

  • Tenda A18, firmware version 15.13.07.09.

Severity

  • CVSS v3.1 Base Score: 9.8 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Check with Tenda for an updated firmware release for the A18 model that addresses this buffer overflow; apply any available patched firmware as soon as it is published.
  • If no patch is available: Do not expose the router’s web management interface to the internet; restrict access to the administrative interface to trusted internal networks only, disable remote management, and place the device behind a firewall or VPN until a fix is released.

How IONIX identifies potentially affected assets

IONIX matches the following signals against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.

  • Page title: Tenda Web Master
  • Raw response body: an anchor element with a brand-related class and a title attribute of Tenda

References

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