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CVE-2026-51684 – Unauthenticated Access Control Bypass (Service State Tampering) – TOTOLINK T6 Firmw

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Summary

CVE-2026-51684 is a critical improper access control vulnerability (CWE-284) in the setStorageCfg function of TOTOLINK T6 router firmware version 4.1.5cu.748_B20211015. The flaw allows unauthenticated remote attackers to alter the router’s storage-related service state by sending a crafted POST request to the device’s CGI endpoint. The vulnerability carries a CVSS v3.1 base score of 9.8 (Critical).

Technical details

  • Root cause: the setStorageCfg function fails to enforce authentication/authorization checks before processing configuration requests.
  • Trigger condition: an attacker sends a crafted HTTP POST request to /cgi-bin/cstecgi.cgi targeting the setStorageCfg action.
  • Attack vector: network-based, no authentication or user interaction required, low attack complexity.
  • Impact: unauthorized attackers can modify storage-related service settings on the device, with the CVSS vector indicating high impact to confidentiality, integrity, and availability.

Affected software

  • TOTOLINK T6, firmware version 4.1.5cu.748_B20211015

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: No official TOTOLINK patch or advisory addressing this specific CVE has been identified at this time. Check TOTOLINK’s official site (totolink.net) for updated firmware for the T6 model and apply any available update that addresses this issue.
  • If no patch is available: Restrict access to the router’s management/CGI interface (/cgi-bin/cstecgi.cgi) to trusted internal networks only, disable remote/WAN administration, and place the device behind a firewall or VPN so it is not directly reachable from the internet.

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.

  • Raw response body: /cgi-bin/cstecgi.cgi
  • Page title: TOTOLINK

References

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How IONIX’s External Exposure Management Platform Detects and Validates
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Map your entire attack surface (continously)

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Monitor for new CVEs

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3

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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

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6

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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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