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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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How IONIX’s External Exposure Management Platform Detects and Validates
Zero-Days to Shrink MTTR

1

Map your entire attack surface (continously)

IONIX uses multi-factor discovery methods, including DNS analysis, certificate mapping, metadata inspection, and more, to automatically map every internet-facing asset across your environment. This includes cloud instances, third-party platforms, shadow IT, and even forgotten infrastructure that traditional tools miss.

2

Monitor for new CVEs

Dozens of threat intel feeds using agentic technology are continuously analyzed to detect the appearance of proof-of-concept code, exploit kits, and indicators of active targeting. IONIX goes further by applying AI to proactively evaluate whether emerging vulnerabilities are likely to be exploited, even before PoCs go public.

3

Identify Potential External Exposures

Not all CVEs matter. IONIX filters vulnerabilities by asking attacker-centric questions: Can it be reached from the internet? Does it require authentication? Is it being exploited in the wild? This dramatically reduces noise and focuses teams on threats that can actually be weaponized.

4

Create Safe, Scalable Exploit Validations

IONIX transforms real-world PoCs into safe, non-intrusive test payloads that can be run in production environments without disruption. These simulations are precisely targeted to the systems that are vulnerable, ensuring rapid validation without unnecessary load.

5

Execute Exploit Validations

By combining context about software stack, versioning, exposure status, and reachability, IONIX ensures that only the right payloads are executed against the right assets, maximizing efficiency and minimizing risk.

6

Drive Fast and Actionable Remediation

Results are routed through integrations with ticketing, SOAR, and SIEM tools. Issues are written in plain language, bundled into remediation clusters, and prioritized based on asset criticality, exploitability, and blast radius. This shortens mean time to remediation (MTTR) and empowers teams to act with confidence.

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