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CVE-2026-51736 – Unauthenticated System Log Erasure – TOTOLINK T6 4.1.5cu.748_B20211015

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Summary

CVE-2026-51736 is an improper access control vulnerability (CWE-284) in the clearSyslog function of the TOTOLINK T6 router web management interface, firmware version 4.1.5cu.748_B20211015. The flaw allows a remote, unauthenticated attacker to erase the device’s system logs by sending a crafted POST request to the /cgi-bin/cstecgi.cgi endpoint. The issue carries a CVSS v3.1 base score of 9.1 (Critical).

Technical details

  • Root cause: The clearSyslog function does not verify that the requester is authenticated before executing the log-clearing operation.
  • Trigger conditions: An attacker sends a specially crafted HTTP POST request to /cgi-bin/cstecgi.cgi targeting the clearSyslog action; no session, credentials, or prior access is required.
  • Attack vector: Network-based, low attack complexity, no privileges required, no user interaction.
  • Impact: Successful exploitation lets an unauthenticated attacker erase system logs, undermining forensic visibility and log integrity on the affected device, which can be used to conceal follow-on malicious activity on the router.

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 patch has been confirmed as available for this specific firmware build at time of writing; check the TOTOLINK support/download portal for a firmware update addressing this issue and apply it as soon as it is released.
  • If no patch: Restrict access to the router’s web management interface (/cgi-bin/cstecgi.cgi) to trusted internal networks only, disable remote/WAN-side administration, and place the device behind a firewall or VPN so it is not directly internet-exposed. Monitor for unexpected log gaps that could indicate exploitation attempts.

References

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