CVE-2026-51621 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getInitCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain sensitive device configuration information via sending a crafted POST request to /cgi-bin/cstecgi.cgi.
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Analysis
by VulDB Data Team • 08/28/2026
The vulnerability identified in the TOTOLINK T6 router, specifically within firmware version 4.1.5cu.748_B20211015, represents a critical failure in access control mechanisms governing sensitive administrative functions. This flaw is located within the getInitCfg function, which is designed to retrieve initial configuration data from the device. The core technical issue stems from an insufficient validation of authentication tokens or session states when processing incoming HTTP POST requests directed at the /cgi-bin/cstecgi.cgi endpoint. In a properly secured system, this specific CGI script should require valid administrative credentials before returning any internal configuration parameters. However, due to the incorrect access control logic, the application fails to enforce these prerequisites, effectively leaving the function accessible to unauthenticated actors. This allows an attacker who has network connectivity to the router's management interface to bypass authentication entirely and extract comprehensive device settings without prior authorization.
From a technical perspective, this vulnerability is classified under CWE-284, which describes Improper Access Control, specifically highlighting failures in enforcing restrictions on authenticated users or unauthenticated actors accessing sensitive resources. The attack vector involves sending a crafted POST request to the specified CGI endpoint. Because the getInitCfg function does not adequately verify the identity of the requester, it proceeds to execute and return data that is intended for authorized administrators only. This often includes network configuration details such as SSID names and passwords, WAN settings, DNS configurations, firewall rules, and potentially administrative login credentials if they are stored in plain text or weakly encrypted formats within the initial config dump. The ability to retrieve this information remotely makes it particularly dangerous, as it does not require physical access to the device once network exposure is established.
The operational impact of this vulnerability is severe, primarily because it facilitates a significant loss of confidentiality for the router's configuration data. An attacker can use the obtained sensitive information to map out the internal network topology, identify connected devices, and understand security policies in place. This intelligence gathering phase often precedes more destructive attacks. For instance, knowledge of Wi-Fi passwords allows an attacker to join the local area network, potentially leading to lateral movement against other vulnerable hosts on the same subnet. Furthermore, if administrative credentials are exposed, the attacker gains full control over the device, enabling them to modify settings, redirect traffic through malicious DNS servers for phishing or man-in-the-middle attacks, or disable security features entirely. This aligns with ATT&CK technique T1078, Valid Accounts, as the attacker effectively exploits a lack of proper session management to assume an administrative role without valid credentials, and T1506, Post-Compromise Discovery, by enumerating system configuration data.
Mitigation strategies for this vulnerability focus on both immediate remediation and long-term security hardening. The most effective solution is to apply the firmware update provided by TOTOLINK that addresses the access control flaw in the getInitCfg function. If an official patch is not immediately available or applicable, administrators should restrict network access to the router's management interface by placing it behind a firewall rule that only allows connections from trusted IP addresses or VLANs. Additionally, changing default administrative passwords and ensuring they are complex can reduce the risk if other authentication bypasses exist in different parts of the firmware. It is also advisable to disable remote management features unless absolutely necessary, as this limits the attack surface exposed to external networks. Regularly auditing router configurations for sensitive data exposure and keeping all connected devices updated further reduces the potential impact should such vulnerabilities be exploited in the future.