CVE-2026-51635 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getWiFiScheduleCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain 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 the TOTOLINK T6 router, specifically within firmware version 4.1.5cu.748_B20211015, represents a critical failure in access control mechanisms governing sensitive configuration data. The flaw resides in the getWiFiScheduleCfg function, which is responsible for retrieving Wi-Fi scheduling configurations from the device's internal settings. This component fails to enforce proper authentication or authorization checks before processing incoming requests. Consequently, any actor with network connectivity to the router can interact with this endpoint without providing valid credentials, effectively bypassing the intended security boundaries designed to protect administrative and operational data.
From a technical perspective, the exploitation vector involves sending a specifically crafted POST request to the /cgi-bin/cstecgi.cgi interface. This CGI script acts as an intermediary between web-based management interfaces or external scripts and the router's underlying firmware logic. By targeting this specific endpoint with a malformed or unauthenticated payload directed at the getWiFiScheduleCfg function, an attacker can trigger the retrieval of Wi-Fi scheduling rules. These rules typically dictate when wireless networks are enabled or disabled for different SSIDs, often including details about channel selection, transmission power levels, and time-based access controls. The lack of input validation and session verification allows this information to be returned in plain text within the HTTP response body.
The operational impact of this vulnerability extends beyond simple data leakage. Wi-Fi scheduling configurations can reveal significant insights into an organization's or individual user's network usage patterns and security posture. For instance, knowing when wireless networks are active helps attackers determine optimal windows for conducting unauthorized scans, man-in-the-middle attacks, or brute-force attempts against connected devices. Furthermore, if the schedule includes specific SSID names associated with corporate environments or IoT device groups, it aids in reconnaissance efforts by mapping out potential targets based on their operational hours and network segmentation strategies. This information is particularly valuable during the initial phases of an attack lifecycle where situational awareness is paramount for planning subsequent exploitation steps.
This vulnerability aligns closely with CWE-284, which describes Improper Access Control, as it involves a failure to restrict access to resources that should be protected by authentication mechanisms. Additionally, from the perspective of the MITRE ATT&CK framework, this flaw facilitates the Reconnaissance phase (T1592) and potentially Collection if combined with other exploits, allowing adversaries to gather information about network configurations without detection or authorization. The ability to extract configuration data remotely underscores a fundamental design weakness in how sensitive management functions are exposed through web interfaces on embedded IoT devices.
Mitigation strategies for this vulnerability primarily involve immediate firmware updates provided by the vendor, which should include proper authentication checks within the getWiFiScheduleCfg function and stricter validation of incoming POST requests. In environments where patching is not immediately feasible, network segmentation can help isolate vulnerable routers from untrusted networks, ensuring that only authorized management stations have access to the administrative interface. Additionally, disabling remote management features if they are not strictly necessary reduces the attack surface by preventing external actors from reaching the /cgi-bin/cstecgi.cgi endpoint altogether. Regular security audits and penetration testing of IoT devices can help identify similar misconfigurations before they are exploited in the wild.