CVE-2026-51670 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the getSlaveUpdate function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to query slave upgrade status and affect upgrade bookkeeping 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 getSlaveUpdate function, which is exposed through the CGI script located at /cgi-bin/cstecgi.cgi. This architectural weakness allows unauthenticated actors to interact with internal system functions that should be restricted to authorized administrators or authenticated users only. The core issue stems from a lack of proper authentication checks before processing requests directed toward this specific endpoint, effectively bypassing security controls designed to protect sensitive operational data and state management processes.
From a technical perspective, the vulnerability enables remote attackers to send crafted POST requests to the designated CGI script without providing valid credentials or session tokens. By exploiting this misconfiguration, an attacker can query the current status of slave device upgrades within a mesh network topology managed by the router. This capability reveals internal operational states that are not intended for public disclosure, potentially exposing details about connected devices and their firmware versions. Furthermore, the ability to affect upgrade bookkeeping implies that attackers may manipulate or disrupt the tracking mechanisms used by the system to manage firmware updates across multiple nodes in a mesh network.
The operational impact of this vulnerability is significant as it compromises both confidentiality and integrity within the local network environment. The disclosure of slave upgrade status can aid adversaries in reconnaissance efforts, allowing them to identify specific devices running outdated or vulnerable firmware versions that may be targeted for subsequent exploitation. Additionally, the ability to interfere with upgrade bookkeeping could lead to denial-of-service conditions by corrupting update records or preventing legitimate updates from being processed correctly. This disruption undermines the reliability of network maintenance operations and leaves connected devices in a potentially insecure state if they fail to receive necessary security patches due to manipulated status tracking.
This flaw aligns closely with CWE-284, which describes Improper Access Control vulnerabilities where insufficient restrictions are applied to actions performed by authenticated or unauthenticated users. In the context of modern attack frameworks, this behavior corresponds to ATT&CK technique T1078, specifically relating to Valid Accounts and Default Credentials if authentication is bypassed entirely, as well as aspects of reconnaissance through information discovery. The exploitation vector highlights the risks associated with exposing internal management functions via web interfaces without rigorous input validation and authorization checks.
To mitigate this vulnerability, users should immediately update their TOTOLINK T6 firmware to a patched version that addresses these access control deficiencies. Network administrators must ensure that remote management features are disabled unless absolutely necessary, as restricting external access reduces the attack surface available for such exploits. Additionally, implementing network segmentation can limit lateral movement and protect critical infrastructure components from unauthorized interaction with vulnerable endpoints. Regular audits of web application security controls and adherence to secure coding practices during firmware development are essential to prevent similar misconfigurations in future releases.