CVE-2026-51710 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the setParentalRules function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to alter parental-control behavior 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 setParentalRules function of TOTOLINK T6 router firmware version 4.1.5cu.748_B20211015 represents a critical failure in access control mechanisms, specifically classified under CWE-284: Improper Access Control. This flaw allows unauthenticated attackers to manipulate parental control settings by sending crafted POST requests to the /cgi-bin/cstecgi.cgi endpoint. The root cause lies in the application's insufficient validation of user privileges before executing administrative functions that modify system configuration parameters. In a properly secured environment, any request intended to alter critical security or filtering rules must be authenticated and authorized through verified session tokens or credentials. However, in this specific firmware version, the backend logic fails to enforce these checks, effectively treating requests from unauthenticated sources with the same level of trust as those from legitimate administrators.
From a technical perspective, the /cgi-bin/cstecgi.cgi interface serves as the primary gateway for managing various router functionalities via Common Gateway Interface scripts. The setParentalRules function within this script is designed to update filtering rules that restrict internet access based on time or website categories. Due to the missing authentication check, an attacker can exploit this by crafting a specific HTTP POST request containing malicious parameters that redefine these parental control profiles. This could involve disabling restrictions entirely, allowing unrestricted access for all devices connected to the network, or conversely, blocking legitimate traffic arbitrarily. The ability to modify these rules without authorization undermines the integrity of the router's security posture and its intended role as a gatekeeper for network content filtering.
The operational impact of this vulnerability is significant, particularly in home and small office environments where parental controls are often relied upon for safety and productivity management. An attacker with local network access can exploit this flaw to bypass content filters, potentially exposing users to inappropriate or malicious online content. Furthermore, the ability to alter these settings without detection means that an adversary could maintain persistent unauthorized control over network policies even after legitimate administrators have attempted to secure them. This lack of auditability and enforcement creates a blind spot in the security architecture, allowing for silent manipulation of network behavior which can be leveraged for further attacks or simply as a nuisance disruption service against the device owner.
This vulnerability aligns with MITRE ATT&CK technique T1548.002: Abuse Elevation Control Mechanism, where an attacker abuses mechanisms designed to control access levels by bypassing authentication requirements. It also relates to CWE-798: Use of Hard-coded Credentials if the lack of session validation implies a broader pattern of weak security implementation in the firmware's CGI handling logic. The exploitation requires no prior authentication, making it accessible to any entity capable of reaching the router on the local network segment, which significantly lowers the barrier for entry compared to remote code execution vulnerabilities that require complex payload construction or specific user interactions.
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. Until an official patch is available, network administrators can implement compensating controls such as isolating management interfaces from untrusted networks and restricting access to the router's administrative web interface using firewall rules that limit source IP addresses to known trusted hosts only. Additionally, enabling strong WPA3 encryption for Wi-Fi connections reduces the likelihood of unauthorized local network access, thereby limiting the attack surface available to potential exploiters who rely on proximity or local connectivity to send crafted POST requests to the vulnerable CGI endpoint.