CVE-2026-51730 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the delWiFiAclRules function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to remove Wi-Fi ACL rules via sending a crafted POST request to /cgi-bin/cstecgi.cgi.
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Analysis
by VulDB Data Team • 08/31/2026
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 network security configurations. The flaw resides in the delWiFiAclRules function, which is responsible for deleting Access Control List rules that restrict or permit device connectivity to the wireless network. This function fails to enforce proper authentication checks before executing state-changing operations on the router's configuration database. Consequently, any entity capable of reaching the web management interface can manipulate these security settings without providing valid credentials, effectively bypassing the intended administrative boundaries established by the vendor.
From a technical perspective, this vulnerability is classified as an improper access control issue, aligning with CWE-269 in the Common Weakness Enumeration taxonomy. The exploitation vector involves sending a crafted POST request to the endpoint /cgi-bin/cstecgi.cgi. This CGI script acts as the interface between the web server and the router's backend processes. By manipulating parameters within this HTTP POST payload, an attacker can invoke the delWiFiAclRules function directly. Since the application does not verify if the requester has authenticated administrative privileges before processing the deletion request, it allows for unauthorized modification of critical security policies. This type of flaw is often referred to as a broken access control vulnerability and is frequently exploited in conjunction with other weaknesses such as insecure direct object references or lack of session management validation.
The operational impact of this vulnerability is severe because Wi-Fi Access Control Lists are primary defense mechanisms against unauthorized network access. By removing these rules, an attacker can effectively disable the whitelist or blacklist protections that prevent rogue devices from connecting to the local area network. This action opens the door for further exploitation, including lateral movement within the internal network, eavesdropping on unencrypted traffic, and potential compromise of other connected IoT devices or workstations. In environments where strict segmentation is required for compliance with standards like PCI DSS or HIPAA, this vulnerability undermines the integrity of the security posture by allowing an external actor to erase audit trails and access restrictions remotely.
This behavior maps directly to several techniques in the MITRE ATT&CK framework, particularly T1548.002 Abuse Elevation Control Mechanism for privilege escalation through misconfigured ACLs, and more broadly under T1136.001 Internal Credential Access if used to facilitate further credential harvesting after network access is gained. The ability to modify security configurations without authentication also falls under the broader category of Defense Evasion techniques where an attacker alters system settings to avoid detection or maintain persistence.
Mitigation strategies for this vulnerability should prioritize immediate patching by updating the router firmware to a version that addresses these access control checks. If upgrading is not immediately feasible, network segmentation can help isolate the management interface from untrusted networks. Additionally, administrators should ensure that remote administration features are disabled unless absolutely necessary and enforce strong, unique passwords for all administrative accounts. Implementing Web Application Firewalls with rules specifically targeting malformed or unauthorized POST requests to CGI endpoints may also provide a layer of defense against exploitation attempts while permanent fixes are deployed. Regular audits of configuration files and monitoring for unexpected changes in ACL settings can aid in early detection of such attacks.