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CVE-2026-51675 – Unauthenticated WAN Reconfiguration – TOTOLINK T6 4.1.5cu.748_B20211015

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Summary

CVE-2026-51675 is an incorrect access control vulnerability (CWE-284) in the setWanIeCfg function of the TOTOLINK T6 router’s web management interface. Unauthenticated attackers can send a crafted POST request to /cgi-bin/cstecgi.cgi to reconfigure the device’s WAN/uplink settings without providing credentials. The flaw carries a CVSS v3.1 base score of 9.1 (Critical).

Technical details

  • Root cause: The setWanIeCfg function fails to enforce authentication or session validation before processing requests that modify WAN uplink configuration.
  • Trigger condition: An attacker sends a specially crafted HTTP POST request to the /cgi-bin/cstecgi.cgi endpoint invoking the setWanIeCfg action.
  • Attack vector: Network-based, requiring no user interaction and no privileges (AV:N/AC:L/PR:N/UI:N).
  • Impact: Unauthorized attackers can alter the router’s uplink/WAN configuration, resulting in high confidentiality and integrity impact; availability impact is not indicated in the scoring.

Affected software

  • TOTOLINK T6, firmware version 4.1.5cu.748_B20211015

Severity

  • CVSS v3.1 Base Score: 9.1 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Mitigation and recommended actions

  • Immediate: No vendor-supplied patched firmware version is currently confirmed in public records for this vulnerability. Check TOTOLINK’s official firmware download page for the T6 model to confirm whether an updated build superseding 4.1.5cu.748_B20211015 has been released, and apply it as soon as it is available.
  • If no patch is available: Restrict access to the router’s web management interface (/cgi-bin/cstecgi.cgi) to trusted internal networks only, disable remote/WAN-side management, 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, a firmware-version string in the form N600R (Firmware version V...), TOTOLINK

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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  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
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