CVE-2026-51669 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the getPairCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain pairing and mesh-slave configuration 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 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 getPairCfg function, which is designed to retrieve configuration data related to mesh networking and pairing settings. Under normal operational conditions, such sensitive administrative functions should require authentication to prevent unauthorized users from accessing or modifying network topology details. However, due to insufficient validation of user credentials before processing requests directed at this specific endpoint, an unauthenticated attacker can successfully interact with the function without providing valid login information.
The technical mechanism of exploitation involves sending a crafted POST request to the /cgi-bin/cstecgi.cgi script, which serves as the gateway for executing various administrative commands on the router's embedded web server. By targeting the getPairCfg endpoint through this interface, an attacker can bypass authentication checks entirely. This lack of proper authorization enforcement allows external actors to extract detailed configuration data that includes pairing keys and mesh-slave configurations. These parameters are essential for maintaining secure communication between nodes in a mesh network, making their exposure particularly dangerous as it compromises the integrity of the entire local area network infrastructure managed by the device.
From an operational impact perspective, this vulnerability enables significant reconnaissance and potential lateral movement within a protected network environment. The disclosure of pairing configurations reveals how devices are authenticated to join the mesh system, potentially allowing attackers to impersonate legitimate nodes or disrupt network stability by injecting rogue devices. Furthermore, knowledge of these internal configuration structures can aid in crafting more sophisticated attacks against other components of the router's firmware that may rely on similar assumptions about secure access controls. This aligns with Common Weakness Enumeration (CWE) category CWE-284, which describes Improper Access Control, and maps to MITRE ATT&CK technique T1078, Valid Accounts, as it involves exploiting misconfigured permissions rather than stealing credentials directly.
Mitigation strategies for this vulnerability primarily involve applying the latest firmware updates provided by TOTOLINK, if available, which should address the missing authentication checks in the getPairCfg function. In environments where immediate patching is not feasible, network segmentation can help isolate vulnerable devices from critical assets to limit potential exploitation impact. Additionally, administrators should ensure that remote management features are disabled unless strictly necessary and enforce strong password policies for any remaining accessible administrative interfaces. Regular auditing of web server configurations and implementing strict input validation on all CGI endpoints can further reduce the attack surface associated with such access control failures.