CVE-2026-51650 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getRemoteCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain remote-management enablement and port information 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 getRemoteCfg function, which is invoked when processing requests directed to the /cgi-bin/cstecgi.cgi endpoint. This component is designed to retrieve configuration details regarding remote management settings, including whether remote administration is enabled and on which port it operates. Under normal operational conditions, such sensitive administrative queries should require valid authentication credentials or session tokens to prevent unauthorized users from accessing internal network configurations. However, the implementation fails to enforce these security controls effectively, allowing unauthenticated actors to interact with this function directly through standard HTTP POST requests.
From a technical perspective, the root cause of this vulnerability is an improper authorization check within the server-side logic handling the cstecgi.cgi script. The application does not verify whether the incoming request originates from an authenticated session or possesses valid administrative privileges before returning sensitive configuration data. This oversight allows any external entity with network connectivity to the router's management interface, regardless of their authentication status, to query and receive detailed information about the remote access capabilities of the device. By sending a crafted POST request to the specified endpoint, attackers can extract precise details such as whether remote login is active and the specific port number assigned for it. This type of flaw aligns with CWE-284, which classifies Improper Access Control, indicating that the system fails to restrict access to resources or functions based on user roles or authentication states.
The operational impact of this vulnerability extends beyond simple information disclosure. While obtaining remote management settings might seem like a low-severity issue in isolation, it serves as a critical reconnaissance step for subsequent attacks. Knowledge of whether remote administration is enabled and the specific port used allows attackers to tailor their exploitation strategies accordingly. If remote access is active on an exposed port, this vulnerability significantly lowers the barrier for further compromise by enabling targeted brute-force attacks against administrative credentials or facilitating man-in-the-middle attacks if weak encryption protocols are in use. Furthermore, it aids in mapping the attack surface of home and small business networks where such routers are commonly deployed as gateways. This behavior is consistent with ATT&CK technique T1046, Network Service Discovery, specifically within the context of service enumeration on network devices, which adversaries frequently employ to identify potential entry points for lateral movement or data exfiltration.
Mitigation strategies must address both immediate remediation and long-term security posture improvements. The primary solution is to apply the firmware update provided by TOTOLINK that patches this specific access control flaw in the getRemoteCfg function. Administrators should ensure their devices are running the latest stable release where authentication checks have been properly enforced for all administrative endpoints. In cases where immediate patching is not feasible, network-level controls can serve as a temporary compensating measure. This includes restricting access to the router's management interface via firewall rules that limit connectivity to trusted IP addresses only and disabling remote administration entirely if it is not strictly required for business operations. Additionally, enforcing strong password policies and enabling multi-factor authentication where supported by the firmware can reduce the risk of exploitation even if configuration details are leaked. Regular auditing of connected devices and monitoring for unusual outbound traffic patterns related to management interfaces can also help detect potential attempts at exploiting this vulnerability before significant damage occurs.