CVE-2026-51736 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the clearSyslog function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to erase system logs via sending a crafted POST request to /cgi-bin/cstecgi.cgi.
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Analysis
by VulDB Data Team • 08/31/2026
The vulnerability identified in the clearSyslog function of TOTOLINK T6 router firmware version 4.1.5cu.748_B20211015 represents a critical failure in access control mechanisms within the device's web management interface. This flaw specifically affects the CGI script located at /cgi-bin/cstecgi.cgi, which is responsible for handling various administrative tasks including log management. The core technical issue lies in the absence of proper authentication checks or session validation when processing requests directed to this specific endpoint. Consequently, any actor with network access to the router's web interface can invoke the clearSyslog function without providing valid credentials. This lack of enforcement allows unauthenticated users to execute administrative commands that should be restricted to authorized personnel only, fundamentally undermining the integrity and security posture of the device.
From a technical perspective, this vulnerability is classified under CWE-284, which denotes Improper Access Control. The flaw arises because the application logic fails to verify the identity or privilege level of the user making the request before performing sensitive operations. By sending a crafted POST request to the specified CGI endpoint, an attacker can trigger the deletion of system logs stored on the device. This action is not merely cosmetic; it directly impacts the operational integrity of the router by removing critical audit trails that record network events, connection attempts, and potential security incidents. The ability to erase these logs indicates a severe breakdown in the principle of least privilege, where actions requiring high-level permissions are accessible to unauthenticated entities.
The operational impact of this vulnerability is significant for both individual users and enterprise environments relying on TOTOLINK routers. System logs serve as a primary source of forensic evidence during security investigations. When an attacker can delete these logs, they effectively cover their tracks after performing malicious activities such as unauthorized configuration changes, data exfiltration, or network reconnaissance. This capability facilitates persistence by making it difficult for administrators to detect the intrusion or understand its scope. Furthermore, the loss of log data hampers compliance with regulatory standards that require detailed logging and monitoring of network infrastructure. The vulnerability essentially allows an attacker to disrupt the availability of security information while simultaneously obscuring their presence on the network.
This behavior aligns with several tactics in the MITRE ATT&CK framework, particularly T1070 Indicator Removal, which covers techniques used by adversaries to remove artifacts or operate left behind by previous actions within a compromised environment. It also relates to T1562 Impair Defenses, as disabling logging mechanisms prevents detection and response efforts from functioning correctly. The attack vector is classified under Network-Based exploitation with Low complexity, requiring only network connectivity to the target device's web interface. There are no additional prerequisites such as user interaction or specific software versions beyond the affected firmware build, making this a high-risk vulnerability for any deployed instance of the specified router model that exposes its management interface to untrusted networks.
Mitigation strategies must focus on immediate remediation and long-term security hardening. The most effective solution is to apply the latest firmware update provided by TOTOLINK, which should include patches addressing these access control deficiencies in the CGI scripts. Until an official patch is available or deployed, administrators can implement network-level controls such as firewall rules to restrict access to /cgi-bin/cstecgi.cgi and other administrative endpoints exclusively from trusted IP addresses or management VLANs. Additionally, disabling remote management features if they are not strictly necessary reduces the attack surface exposed to potential attackers. Regular monitoring of router logs for anomalies is also recommended, although this may be challenging given the ability to delete them. Organizations should prioritize replacing affected devices with models that adhere to stricter security standards and implement robust access control policies across all network infrastructure components.