CVE-2026-51622 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getWanCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain WAN configuration data 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 getWanCfg function of TOTOLINK T6 router firmware version 4.1.5cu.748_B20211015 represents a critical failure in access control mechanisms, specifically categorized under CWE-284 Improper Access Control. This flaw allows unauthenticated remote attackers to retrieve sensitive Wide Area Network configuration data by interacting with the device's web interface through a crafted POST request directed at the /cgi-bin/cstecgi.cgi endpoint. The root cause lies in the insufficient validation of authentication tokens or session states before processing requests that query network parameters, effectively bypassing intended security boundaries designed to restrict such information to authorized administrators only.
From an operational perspective, this vulnerability enables attackers to gather detailed insights into the router's network topology and configuration settings without requiring valid credentials. The exposed WAN configuration data typically includes critical elements such as IP address assignments, subnet masks, gateway addresses, DNS server configurations, and potentially PPPoE authentication details or static routing tables depending on the specific implementation of the getWanCfg function. This information is instrumental for attackers planning subsequent stages of an intrusion campaign, as it provides a clear map of how the device connects to external networks and handles traffic flow.
The exploitation of this flaw aligns with ATT&CK technique T1087.004, which involves obtaining local network configuration data from cloud or on-premises infrastructure. By leveraging this unauthenticated access vector, adversaries can perform reconnaissance activities that facilitate lateral movement within a private network segment or enable targeted attacks against other devices connected to the same WAN interface. The ability to extract these configurations remotely significantly lowers the barrier for entry in attack scenarios where physical access is not available, turning what might have been an internal-only administrative function into a remote information disclosure vector accessible over the internet if port forwarding or UPnP rules expose the management interface.
Mitigation strategies must prioritize immediate patching of the firmware to versions that address this specific authentication bypass logic within the CGI script handling WAN configuration queries. In scenarios where updating is not immediately feasible, network-level controls should be implemented to restrict access to the /cgi-bin/cstecgi.cgi endpoint exclusively from trusted management subnets or internal IP ranges using firewall rules. Additionally, disabling remote administration features and ensuring that the web interface is not exposed directly to untrusted networks are essential defensive measures. Regular security audits of embedded device firmware for proper implementation of authentication checks on all administrative endpoints remain crucial to preventing similar access control failures in IoT devices.