CVE-2026-51712 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the setApWiFiSchCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to alter wireless availability windows 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 setApWiFiSchCfg function within TOTOLINK T6 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 permits unauthenticated remote attackers to manipulate wireless availability configurations without requiring valid credentials or session tokens. The attack vector involves sending a specially crafted HTTP POST request directly to the /cgi-bin/cstecgi.cgi endpoint, which serves as the primary interface for managing device settings via Common Gateway Interface scripts commonly found in embedded IoT devices.
From a technical perspective, the setApWiFiSchCfg function is responsible for configuring scheduled wireless availability windows, allowing administrators to define specific time periods during which Wi-Fi services are active or inactive. The absence of authentication checks within this handler means that any entity capable of reaching the device's network interface can modify these parameters. This lack of validation allows an attacker to overwrite existing configuration values with arbitrary data, effectively bypassing intended security boundaries designed to restrict administrative actions to authorized users only.
The operational impact of this vulnerability is significant for both residential and small business environments relying on TOTOLINK routers for connectivity management. By altering wireless availability windows, an attacker can disrupt network access during critical times or create periods where the Wi-Fi signal is unexpectedly disabled, leading to service denial. Furthermore, such manipulation could be used as a precursor to more sophisticated attacks, such as forcing devices into maintenance modes that might expose other unpatched vulnerabilities or facilitate lateral movement within a local area network by manipulating connectivity parameters to isolate specific segments or redirect traffic through compromised nodes.
This type of vulnerability aligns with the MITRE ATT&CK technique T1562.001 Impair Defenses: Disable or Modify Tools, as it allows an adversary to interfere with security-relevant functions like wireless access controls. It also relates to CWE-798 Use of Hard-coded Credentials if the device relies on default configurations that are easily exploitable without prior authentication, although in this specific case, the primary issue is the complete lack of required authentication for a privileged configuration function rather than credential reuse.
Mitigation strategies should prioritize immediate firmware updates provided by TOTOLINK to address the missing access control checks within the CGI script handler. In scenarios where patching is not immediately feasible, network segmentation can help isolate vulnerable devices from critical infrastructure and sensitive data stores. Additionally, implementing strict firewall rules that restrict access to management interfaces like /cgi-bin/cstecgi.cgi to trusted IP addresses only can reduce the attack surface by preventing unauthenticated external actors from reaching the vulnerable endpoint. Regular security audits focusing on authentication requirements for all administrative functions are essential to prevent similar misconfigurations in embedded systems.