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CVE-2026-86165 – Remote Buffer Overflow / Denial of Service – Tenda HG10 Firmware 300001138

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Summary

CVE-2026-86165 is a critical buffer overflow vulnerability in Tenda HG10 firmware (HG7_HG9_HG10re_300001138), an AC1200 dual-band Wi-Fi xPON ONT device. The flaw resides in the formURL function handling the /boaform/admin/formURL endpoint of the device’s Boa web server, where the Keywd/urlFQDN parameters are copied into a fixed-size buffer without adequate length validation. The vulnerability is remotely exploitable without authentication and has a public proof-of-concept exploit available.

Technical details

  • Root cause: The formURL handler uses an unsafe strcpy-style copy operation to move the attacker-controlled Keywd (and urlFQDN) parameter value into a fixed-size stack/heap buffer without bounds checking.
  • Trigger conditions: An attacker sends a crafted POST /boaform/admin/formURL request with an oversized Keywd value (along with addKeywd=Add, submit-url=/url_blocking.asp, and postSecurityFlag parameters) to the device’s management web interface.
  • Attack vector: Network-based; no user interaction and, per the published exploit and reporting, no valid session appears required to reach the vulnerable handler.
  • Impact: Memory corruption leading to denial of service (device becomes unresponsive), with the potential for remote code execution given full compromise of confidentiality, integrity, and availability reflected in the CVSS impact metrics.

Affected software

  • Tenda HG10 firmware version 300001138 (build: HG7_HG9_HG10re_300001138)

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
  • (A CVSS v4.0 score of 9.3, Critical, is also recorded for this CVE.)

Mitigation and recommended actions

  • Immediate: No vendor-supplied patched firmware version has been identified in the available advisory data at time of publication. Check Tenda’s official support channels for a firmware update addressing this issue and apply it as soon as it becomes available.
  • If no patch is available:
    • Disable remote/WAN access to the device’s web management interface; restrict administration to trusted internal networks only.
    • Place management interfaces behind a VPN or firewall ACLs that block unsolicited inbound access to the /boaform/admin/formURL endpoint.
    • Monitor for anomalous large POST requests to /boaform/admin/formURL as a detection signal.
    • Consider replacing or isolating affected devices if they cannot be updated, given the criticality of the flaw.

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 class and title="Tenda"

References

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How IONIX’s External Exposure Management Platform Detects and Validates
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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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