Live Exposure Defense: From CVE to Confirmed Exposure in 12 Hours – See more

Back
New CVE Detected

CVE-2026-51676 – Unauthenticated Access-Device Policy Tampering – TOTOLINK T6 Firmware 4.1.5cu.748_B

Be the first to know when new zero-days emerge:

Subscribe to Email Alerts
Subscribe to RSS Feed

Summary

CVE-2026-51676 is an incorrect access control vulnerability in the setAccessDeviceCfg function of TOTOLINK T6 router firmware version 4.1.5cu.748_B20211015. The flaw allows an unauthenticated, remote attacker to alter access-device policies on the router by sending a crafted POST request to the device’s /cgi-bin/cstecgi.cgi endpoint. It carries a CVSS v3.1 base score of 9.1 (Critical), reflecting network-exploitable, no-authentication-required impact to confidentiality and integrity.

Technical details

  • Root cause: The setAccessDeviceCfg function, exposed via the CGI handler /cgi-bin/cstecgi.cgi, fails to enforce proper authentication/authorization checks before processing requests that modify access-device configuration.
  • Trigger conditions: An attacker sends a specially crafted HTTP POST request to /cgi-bin/cstecgi.cgi invoking the setAccessDeviceCfg action; no valid session or credentials are required.
  • Attack vector: Network-based, requiring only that the device’s management interface be reachable by the attacker (e.g., exposed to the internet or an untrusted network segment). No user interaction is needed.
  • Impact: Unauthenticated attackers can alter access-device policies on the router, undermining device access controls and enabling unauthorized changes to network security posture.

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 has been identified in the public CVE record for this issue. Check the TOTOLINK official downloads page for a firmware update addressing this CVE and apply it as soon as it becomes available.
  • If no patch is available:
    • Restrict access to the router’s web management interface (/cgi-bin/cstecgi.cgi) to trusted internal networks only; do not expose it to the public internet.
    • Place the device behind a VPN or firewall rule limiting management access to authorized administrative hosts.
    • Monitor for unexpected POST requests to /cgi-bin/cstecgi.cgi and for unauthorized changes to access-device configuration.
    • Consider replacing or isolating end-of-life/unsupported TOTOLINK devices running this firmware build where a vendor fix is not forthcoming.

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, TOTOLINK
  • Raw response body (combined with the above): N600R (Firmware version V<version>)

References

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report

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.

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report
Close

Subscribe to Threat Center RSS

Copy/paste the link below into your preferred RSS reader or follow these instructions to subscribe to Slack alerts.

Open RSS feedSlack setup instructions

Close

Get Real-Time CVE Alerts to Your Email

Be the first to know when new zero-days emerge