CVE-2026-51648 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getWanInfo function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain WAN information returned by the endpoint 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 getWanInfo function, which is invoked when an HTTP POST request is directed to the /cgi-bin/cstecgi.cgi endpoint. This architectural weakness allows unauthenticated attackers to retrieve sensitive Wide Area Network configuration details without providing valid credentials or session tokens. In a properly secured system, such administrative functions should be gated behind authentication checks that verify user privileges before processing requests and returning data. The absence of these controls effectively exposes internal network topology information to any external actor with connectivity to the router's management port.
From a technical perspective, this issue is classified under CWE-284, which describes Improper Access Control. The root cause lies in the server-side logic handling the cstecgi.cgi script, where the getWanInfo command does not validate the requester's authentication status prior to executing the data retrieval operation. By sending a crafted POST request with specific parameters associated with this function, an attacker can trigger the execution of the underlying code that queries the router for its current WAN settings. This includes details such as IP addresses assigned by the ISP, subnet masks, gateway information, and potentially DNS server configurations. The lack of input validation combined with missing authorization checks creates a straightforward exploitation path that requires no prior compromise or privilege escalation.
The operational impact of this vulnerability is significant due to the nature of the data exposed. WAN information serves as a foundational element for network reconnaissance. An attacker possessing these details can map the external facing infrastructure, identify potential entry points, and understand how traffic flows between the local area network and the internet. This intelligence facilitates more targeted attacks against other devices on the internal network by revealing routing paths and service configurations. Furthermore, knowledge of WAN settings may aid in crafting spoofed packets or launching man-in-the-middle attacks if combined with other vulnerabilities. The exposure undermines the confidentiality integrity boundary expected from enterprise-grade security appliances, allowing adversaries to build a comprehensive profile of the target environment without triggering intrusion detection systems that rely on authentication failure logs.
This vulnerability aligns with MITRE ATT&CK technique T1046, Network Service Discovery, as it enables an attacker to enumerate network services and configurations remotely. It also relates to CWE-200, Exposure of Sensitive Information to an Unauthorized Actor, highlighting the direct leakage of system state data. The ease of exploitation via a simple HTTP POST request underscores the severity of misconfigured web application logic in embedded devices often deployed with default or weak administrative passwords. Even if strong credentials are set, this specific flaw bypasses them entirely for read-only operations concerning WAN configuration, rendering password strength irrelevant for this particular attack vector.
Mitigation strategies must focus on immediate patching and network segmentation until updates are applied. Users should update the TOTOLINK T6 firmware to a version where access control checks have been properly implemented in the getWanInfo function. If updating is not immediately feasible, restricting administrative interface access through firewall rules or VLAN isolation can limit exposure to untrusted networks. Additionally, disabling remote management features if they are not strictly necessary reduces the attack surface available to external adversaries. Security monitoring should be enhanced to detect unusual POST requests targeting cgi-bin endpoints, particularly those involving information disclosure functions. Regular audits of web application logic in embedded devices are essential to prevent similar access control failures that compromise network visibility and security posture.