CVE-2026-51665 in TOTOLINK
Summary
by MITRE • 08/29/2026
Incorrect access control in the getTracerouteCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain traceroute diagnostic logs via sending a crafted POST request to /cgi-bin/cstecgi.cgi.
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Analysis
by VulDB Data Team • 08/29/2026
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 diagnostic functions. The core technical flaw resides in the getTracerouteCfg function, which is exposed through the device's web management interface via the endpoint /cgi-bin/cstecgi.cgi. This component is designed to retrieve configuration details related to traceroute operations, typically requiring administrative privileges or at least authenticated user access due to its potential sensitivity regarding network topology and internal routing information. However, the implementation fails to enforce proper authentication checks before processing requests directed at this specific function. Consequently, any actor with network connectivity to the router's management interface can interact with this endpoint without providing valid credentials.
From a technical perspective, an unauthenticated attacker can exploit this misconfiguration by sending a crafted POST request directly to /cgi-bin/cstecgi.cgi targeting the getTracerouteCfg operation. The server processes this request and returns sensitive diagnostic logs or configuration data that should be restricted. This behavior indicates a lack of session validation or role-based access control enforcement at the application layer for specific CGI scripts. In many embedded web interfaces, certain administrative functions are inadvertently left accessible to unauthenticated users due to incomplete security hardening during development or deployment. The ability to retrieve traceroute logs allows an attacker to map the internal network structure behind the router, identifying active hosts, gateway configurations, and potentially other connected devices that may have their own vulnerabilities.
The operational impact of this vulnerability is significant for both home and small business environments where such routers are commonly deployed. By obtaining these diagnostic logs, an adversary gains valuable reconnaissance data without triggering authentication failure alerts or requiring brute-force attacks against user credentials. This information can be used to plan further targeted attacks against specific devices on the local network, identify potential entry points into more sensitive internal systems, or understand the network segmentation strategy employed by the organization. The exposure of this data violates the principle of least privilege and undermines the confidentiality guarantees expected from secure network infrastructure. It effectively turns a standard administrative tool into an information disclosure vector for unauthorized parties.
This vulnerability aligns with CWE-284, which describes Improper Access Control, as it involves a failure to restrict access to resources based on user identity or role. Furthermore, in the context of the MITRE ATT&CK framework, this exploit technique corresponds to T1046 Network Service Discovery, specifically leveraging local network services for reconnaissance. The attacker is discovering and analyzing active services and their configurations to build an attack map of the target environment. To mitigate this risk, users should immediately update their TOTOLINK T6 firmware to a version that addresses this access control flaw if such an update is available from the vendor. In cases where patching is not immediately possible, network segmentation strategies can help limit exposure by placing management interfaces in isolated VLANs accessible only from trusted administrative workstations. Additionally, disabling remote management features and restricting HTTP/HTTPS access to local networks only reduces the attack surface presented by this vulnerability.