CVE-2026-51636 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getWiFiAclRules function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain Wi-Fi ACL rules 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 administrative functions. The core technical flaw resides in the getWiFiAclRules function, which is exposed through the device's web management interface via the endpoint /cgi-bin/cstecgi.cgi. This component is designed to retrieve Access Control List rules that dictate network traffic permissions for connected devices. However, the implementation fails to enforce proper authentication checks before processing requests intended to query these sensitive configuration parameters. Consequently, any actor with network access to the router's management interface can interact with this function without providing valid credentials, effectively bypassing the security boundary established by the vendor.
From a technical perspective, this issue classifies as an insecure direct object reference or broken access control vulnerability, aligning closely with CWE-284: Improper Access Control and CWE-862: Missing Authorization. The attacker exploits the lack of session validation or token verification associated with the POST request sent to the specified CGI script. By crafting a specific HTTP POST payload targeting this endpoint, an unauthenticated user can trigger the execution of the getWiFiAclRules function within the router's firmware. This action results in the server returning detailed information about the current Wi-Fi Access Control List configuration directly in the response body. The absence of authentication checks at this entry point indicates a fundamental oversight in the security design phase, where sensitive administrative functions were not properly gated behind an authenticated session state.
The operational impact of this vulnerability is significant for network administrators and end-users relying on TOTOLINK T6 devices for secure connectivity. Wi-Fi ACL rules often contain granular details about which devices are permitted or denied access to specific resources, including IP addresses, MAC addresses, port numbers, and protocol types. Exposure of these rules allows an attacker to map the internal network topology and understand the security policies in place. This intelligence can be leveraged for further attacks, such as identifying high-value targets that may have fewer restrictions or exploiting misconfigurations revealed by the ACL data. Furthermore, knowledge of the access control structure aids attackers in crafting more effective social engineering campaigns or lateral movement strategies within a compromised network segment. The ability to view these rules without authentication undermines the integrity and confidentiality of the device's security posture.
In terms of threat modeling, this vulnerability facilitates reconnaissance activities that are characteristic of early-stage attack patterns described in the MITRE ATT&CK framework under T1046: Network Service Discovery or potentially T1592: Gather Victim Host Information if it leads to deeper system profiling. The exploitation requires no prior authentication, making it a high-risk issue for devices deployed in environments where management interfaces are accessible from untrusted networks or where default credentials might be known but not strictly enforced due to this flaw. Attackers can automate the discovery and extraction of these rules using standard web scraping tools or custom scripts, increasing the likelihood of successful exploitation at scale across vulnerable deployments.
Mitigation strategies for this vulnerability primarily involve applying vendor-provided firmware updates that patch the access control logic in the getWiFiAclRules function. Administrators should verify if a newer firmware version is available from TOTOLINK and apply it promptly to enforce proper authentication checks on all administrative endpoints. In cases where immediate patching is not feasible, network segmentation can be employed to restrict access to the router's management interface exclusively to trusted IP addresses or VLANs. Additionally, disabling remote management features unless absolutely necessary reduces the attack surface by preventing external actors from reaching the vulnerable CGI endpoint. Regular security audits and penetration testing of IoT devices are recommended to identify similar misconfigurations in other administrative functions before they can be exploited by malicious actors seeking unauthorized access to network configurations.