CVE-2026-51713 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the setManualDialCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to manipulate WAN dial state 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 the setManualDialCfg function within TOTOLINK T6 firmware version 4.1.5cu.748_B20211015 represents a critical failure in access control mechanisms, specifically classified under CWE-284 Improper Access Control. This flaw permits unauthenticated remote attackers to manipulate the Wide Area Network dial state of the device by sending crafted POST requests to the /cgi-bin/cstecgi.cgi endpoint. The core technical issue lies in the absence of proper authentication checks or session validation before processing configuration changes related to WAN connectivity settings. By exploiting this weakness, an attacker can alter critical network parameters without possessing valid administrative credentials, effectively bypassing intended security boundaries designed to protect device configuration integrity.
From a functional perspective, the ability to manipulate the WAN dial state allows an adversary to disrupt internet connectivity or redirect traffic through unauthorized means. This could involve forcing the router to disconnect from its current ISP connection, potentially causing a denial of service for legitimate users relying on that network path. Alternatively, it may allow the attacker to configure malicious DNS servers or proxy settings during the reconnection process, facilitating man-in-the-middle attacks or data interception. The operational impact is significant as it compromises both the availability and confidentiality aspects of the network infrastructure managed by this router. Such actions can lead to prolonged service outages if the device enters an unstable state due to invalid configuration parameters introduced via the crafted request.
This vulnerability aligns with ATT&CK technique T1548, specifically Abuse Elevation Control Mechanism or Misconfiguration, as it involves exploiting a misconfigured access control policy to perform unauthorized administrative actions. The exploitation vector is remote and requires no prior authentication, which classifies it under CWE-306 Missing Authentication for Critical Function. Attackers can leverage automated tools to send the malicious POST payload repeatedly, increasing the likelihood of successful manipulation before any potential rate limiting or logging mechanisms might detect the anomaly. The simplicity of the attack method underscores the severity of the oversight in the firmware development lifecycle regarding input validation and privilege verification at critical configuration endpoints.
Mitigation strategies must focus on immediate remediation through vendor-provided patches that enforce strict authentication requirements for all CGI scripts handling sensitive system configurations. Administrators should ensure their devices are updated to a version where access control lists properly restrict unauthenticated access to administrative functions. In the interim, if patching is not immediately feasible, network segmentation can help isolate affected routers from critical internal resources. Additionally, enabling robust logging and monitoring on the management interface can aid in detecting attempts to exploit this vulnerability by identifying unusual POST requests targeting the cstecgi.cgi endpoint with parameters indicative of dial state manipulation. Regular security audits and adherence to secure coding standards that mandate authentication checks before any configuration change are essential to prevent similar access control failures in future firmware releases.