CVE-2026-51703 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the setWiFiScheduleCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to alter when Wi-Fi is available 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 TOTOLINK T6 router firmware version 4.1.5cu.748_B20211015 represents a critical failure in access control mechanisms within the device's web management interface. Specifically, the flaw resides in the setWiFiScheduleCfg function, which is responsible for configuring the scheduled availability of Wi-Fi networks. This component fails to enforce proper authentication or authorization checks before processing configuration changes initiated by remote users. As a result, any unauthenticated attacker who can reach the router over the network can interact with this endpoint without providing valid credentials. The attack vector involves sending a specially crafted POST request to the /cgi-bin/cstecgi.cgi script, which serves as the gateway for executing administrative commands on the device. This lack of authentication bypass allows external actors to modify critical wireless settings that should be restricted to authorized administrators only.
From a technical perspective, this vulnerability is classified under CWE-284, Improper Access Control, and aligns with MITRE ATT&CK technique T1505.003, Web Server Component Installation: CGI Scripts. The root cause lies in the application logic of the Common Gateway Interface script, which processes user input to update system configuration files without verifying the session state or permission levels of the requesting entity. By manipulating parameters within the POST request, an attacker can alter the Wi-Fi schedule settings, effectively determining when the wireless interface is active or disabled. This capability undermines the integrity of the network's operational policies and demonstrates a fundamental weakness in how the firmware handles privileged operations through its web-based management portal.
The operational impact of this vulnerability extends beyond simple configuration changes. An adversary with access to this function can disrupt network availability by disabling Wi-Fi services during critical periods, leading to denial-of-service conditions for legitimate users relying on wireless connectivity. Furthermore, such unauthorized modifications may interfere with security policies that depend on specific scheduling rules, potentially exposing the network to increased risk if certain restrictions are removed or altered maliciously. In environments where automated systems rely on consistent network availability, this disruption can have cascading effects on business operations and IoT device functionality. The ability to alter these settings remotely without authentication significantly lowers the barrier for entry, making it a high-risk issue that requires immediate attention from administrators responsible for maintaining secure home or small office networks.
Mitigation strategies must focus on restricting access to administrative interfaces and ensuring robust input validation within CGI scripts. Administrators should immediately update their TOTOLINK T6 firmware to versions where this flaw has been patched by the vendor, as patching is the most effective remediation step. In cases where updates are not yet available or applicable, network segmentation can be employed to isolate management interfaces from untrusted networks, ensuring that only trusted internal subnets can access administrative endpoints like /cgi-bin/cstecgi.cgi. Additionally, implementing strong authentication mechanisms and enforcing session validation checks on all privileged functions is essential to prevent unauthorized configuration changes. Regular security audits of embedded device firmware should include testing for improper access control flaws in web-based management tools to identify similar vulnerabilities before they are exploited by malicious actors seeking to compromise network integrity or availability.