CVE-2026-51639 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getApWiFiSchCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain AP-specific Wi-Fi scheduling 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 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 getApWiFiSchCfg function, which is responsible for retrieving Access Point Wi-Fi scheduling configuration data. This architectural weakness allows unauthenticated attackers to bypass standard authentication requirements and extract sensitive network configuration details by sending a specifically crafted POST request to the /cgi-bin/cstecgi.cgi endpoint. The existence of this vulnerability underscores significant deficiencies in how the firmware validates user privileges before processing requests that expose internal system states, thereby compromising the integrity of the device's security posture.
From a technical perspective, the core issue is an improper authorization check within the CGI script handling Wi-Fi scheduling queries. In secure implementations, any request to retrieve or modify administrative settings must be preceded by a verified session token or valid credentials. However, in this affected firmware version, the getApWiFiSchCfg function does not enforce such checks effectively. An attacker can interact directly with the underlying Common Gateway Interface endpoint without establishing an authenticated session. By constructing a POST request that targets this specific function, the attacker triggers the execution of code that returns detailed configuration parameters related to Wi-Fi scheduling rules. This behavior indicates that the application logic relies on security through obscurity or lacks explicit role-based access control checks for sensitive administrative endpoints.
The operational impact of this vulnerability is substantial, as it facilitates unauthorized disclosure of network infrastructure details. The extracted AP-specific Wi-Fi scheduling rules may include information about when specific wireless networks are active, which SSIDs are enabled during certain time windows, and potentially other configuration parameters that define the behavior of the access point. While these data points might not directly expose passwords or encryption keys in this specific instance, they provide attackers with valuable intelligence for further reconnaissance. Knowledge of Wi-Fi schedules can aid in planning targeted attacks against devices connected to the network when security measures are perceived to be weaker during scheduled off-hours or maintenance windows. Furthermore, understanding the exact configuration allows an attacker to tailor subsequent exploits more effectively, potentially leading to broader compromise if combined with other vulnerabilities such as command injection or buffer overflows that might exist elsewhere in the firmware stack.
This vulnerability aligns closely with CWE-284, which describes Improper Access Control, and falls under the ATT&CK technique T1078, Valid Accounts, although in this case it specifically relates to bypassing authentication entirely rather than misusing valid credentials. The exploitation vector is classified as Network-based (T1059), allowing remote execution without physical access or prior compromise of user accounts. To mitigate this risk, users should immediately update their TOTOLINK T6 firmware to the latest version released by the vendor, which likely includes patches for these authorization checks. If updating is not immediately possible, administrators can attempt to restrict access to the management interface by placing it behind a firewall rule that limits IP addresses or requires VPN connectivity before reaching the web server. Additionally, disabling remote management features if they are not strictly necessary reduces the attack surface exposed to untrusted networks. Regular security audits and penetration testing of IoT devices are recommended to identify similar misconfigurations in access control logic across other network infrastructure components.