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CVE-2026-85109 – Remote Buffer Overflow / DoS (potential RCE) – Tenda HG10 (firmware HG7_HG9_HG10re_

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Summary

CVE-2026-85109 is a buffer overflow vulnerability in the formLogin function of the Boa web server component in Tenda HG10 firmware version 300001138. Remote, unauthenticated attackers can send a crafted Username parameter to /boaform/formLogin to overflow a fixed-size buffer, with confirmed denial-of-service impact and potential for remote code execution. The exploit has been publicly disclosed.

Technical details

  • Root cause: The formLogin handler copies the attacker-supplied Username value into a fixed-size buffer without validating its length, consistent with use of an unsafe copy operation (e.g., strcpy-style handling) that does not check destination capacity.
  • Trigger condition: Sending an HTTP POST request to /boaform/formLogin on the device’s Boa web server with an oversized Username argument.
  • Attack vector: Network-based; no authentication or user interaction is required to reach the vulnerable endpoint.
  • Impact: Publicly available testing shows the overflow crashes/hangs the router (denial of service); given the memory corruption primitive, remote code execution is possible depending on memory layout and runtime protections.

Affected software

  • Tenda HG10 — firmware version 300001138 (Boa Web Server component)

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
  • CVSS v4.0 Score: 9.3 (Critical) — Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Mitigation and recommended actions

  • Immediate: No vendor patch has been publicly disclosed for firmware 300001138 at this time. Check Tenda’s official support channels for an updated firmware release for the HG10 model and apply it as soon as it becomes available.
  • If no patch is available:
    • Disable remote/WAN access to the router’s web management interface (/boaform/* endpoints).
    • Restrict access to the device’s management interface to trusted internal networks only, using firewall rules or network segmentation.
    • Monitor for anomalous or oversized login requests to /boaform/formLogin.
    • Consider replacing end-of-life or unsupported Tenda HG10 devices if no fix is issued by the vendor.

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 (HTML): an anchor element with a class containing brand and title="Tenda"

References

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