CVE-2026-51684 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the setStorageCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to alter the storage-related service state 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 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. Specifically, the flaw resides in the setStorageCfg function, which is responsible for configuring storage-related services such as USB sharing or network attached storage settings. This misconfiguration allows unauthenticated attackers to manipulate these service states without providing valid administrative credentials. The attack vector involves sending a crafted HTTP POST request directly to the /cgi-bin/cstecgi.cgi endpoint, bypassing standard authentication checks that should restrict access to authorized users only.
From a technical perspective, this issue is classified under CWE-284, which describes Improper Access Control. In typical router architectures, configuration changes require session validation and privilege verification before any state-altering operations are executed. However, in this specific firmware version, the server-side logic fails to enforce these security checks for the setStorageCfg function. This oversight enables an attacker who has network access to the management interface to toggle storage services on or off, modify sharing permissions, or potentially expose sensitive data stored on connected USB drives to unauthorized parties. The lack of authentication creates a direct path for privilege escalation from unauthenticated status to administrative control over specific device functions.
The operational impact of this vulnerability is significant, particularly in environments where the router's web interface is exposed to local networks without additional security layers such as VLAN segmentation or firewall rules restricting access to trusted IP ranges. An attacker exploiting this flaw can disrupt network operations by disabling storage services that critical applications depend on. Furthermore, if USB sharing features are enabled via this vulnerability, sensitive files stored on external drives may become accessible over the network without proper encryption or authentication, leading to potential data leakage and privacy violations. In more advanced attack scenarios, manipulating these configurations could serve as a stepping stone for further exploitation of other vulnerabilities within the router's firmware stack.
This type of access control bypass is frequently associated with MITRE ATT&CK technique T1078, specifically Valid Accounts or Default Accounts if default credentials are also weak, but in this case, it aligns more closely with unauthorized configuration changes that can lead to service disruption or data exposure. The vulnerability highlights the importance of rigorous input validation and strict enforcement of authentication policies on all administrative endpoints within embedded systems.
To mitigate this risk, users should immediately update their TOTOLINK T6 firmware to a version where this access control flaw has been patched by the vendor. If an immediate patch is unavailable, network administrators should implement compensating controls such as restricting access to the router's management interface through firewall rules that limit connectivity to trusted IP addresses only. Additionally, disabling remote management features and ensuring that default passwords are changed can reduce the attack surface. Regular security audits of embedded device configurations and adherence to secure coding practices during firmware development are essential preventive measures against similar vulnerabilities in IoT devices.