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CVE-2026-51715 – Unauthenticated MAC Filter Rule Deletion – TOTOLINK T6 4.1.5cu.748_B20211015

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Summary

CVE-2026-51715 is an incorrect access control vulnerability in the delMacFilterRules function of the TOTOLINK T6 router’s web management interface (firmware 4.1.5cu.748_B20211015). It allows a remote, unauthenticated attacker to remove configured MAC filter rules by sending a crafted POST request to /cgi-bin/cstecgi.cgi. The flaw carries a CVSS v3.1 base score of 9.8 (Critical).

Technical details

  • Root cause: the delMacFilterRules handler exposed via /cgi-bin/cstecgi.cgi does not enforce session/authentication checks before processing requests that delete MAC filter rules.
  • Trigger conditions: an attacker sends a crafted HTTP POST request containing the delMacFilterRules action/topic to the device’s CGI endpoint; no valid credentials or prior session are required.
  • Attack vector: Network — the web management interface must be reachable over the network (including the internet, if exposed).
  • Impact: an unauthenticated attacker can remove MAC address filtering rules, weakening the device’s access-control posture and potentially allowing unauthorized devices onto the network. The associated CVSS vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) reflects high confidentiality, integrity, and availability impact.

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: Check the TOTOLINK support/download site for a firmware update addressing this vulnerability for the T6 model and apply it as soon as it is available; no patched version was confirmed at the time of publication.
  • If no patch is available: Restrict access to the router’s web management interface to trusted internal networks only (disable remote/WAN administration), place the device behind a firewall or VPN, and monitor for unexpected changes to MAC filter configurations.

References

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