CVE-2026-51630 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getDdnsCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain DDNS configuration, including domain, username, and password, 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 getDdnsCfg function, which is responsible for retrieving Dynamic DNS configuration details from the system. This component fails to enforce proper authentication checks before processing requests intended to expose sensitive network settings. As a result, any unauthenticated actor capable of reaching the router’s administrative endpoint can exploit this misconfiguration to extract confidential information without providing valid credentials or session tokens.
The technical mechanism of exploitation involves sending a specifically crafted POST request to the /cgi-bin/cstecgi.cgi script on the target device. This CGI interface serves as the bridge between the web server and the underlying system configuration database. By targeting the getDdnsCfg function through this endpoint, an attacker can bypass standard security gates that should verify user privileges. The lack of input validation or permission verification allows external entities to query internal state variables directly, leading to a complete disclosure of Dynamic DNS parameters. These parameters typically include the assigned domain name, as well as the username and password associated with the DDNS service provider account linked to the router.
The operational impact of this vulnerability is severe due to the sensitive nature of the exposed data. Dynamic DNS credentials are often used by home users or small businesses to maintain a consistent hostname for remote access services such as SSH, RDP, or web servers hosted behind NAT. If an attacker obtains these credentials, they can hijack the DDNS service account, potentially redirecting traffic intended for legitimate users to malicious infrastructure. Furthermore, knowledge of the domain name allows attackers to identify active targets more easily and may facilitate further attacks against remote services exposed through that domain. This constitutes a significant risk to confidentiality and integrity, as it enables unauthorized access to connected devices or networks relying on this configuration.
From a classification perspective, this issue aligns with CWE-284, which describes Improper Access Control, specifically where insufficient authorization checks allow unauthenticated users to perform privileged actions. In the context of the MITRE ATT&CK framework, this vulnerability supports techniques related to Discovery and Credential Access, as it allows an adversary to gather information about network configuration and potentially steal credentials for remote access services. The attack vector is classified as Network-based with Low Complexity, requiring no prior authentication or physical proximity beyond logical connectivity to the router’s management interface.
Mitigation strategies should prioritize immediate patching of the firmware to a version where this access control flaw has been resolved by the vendor. In cases where updating is not immediately feasible, network segmentation can limit exposure by restricting access to the router's administrative interface only from trusted internal subnets. Additionally, disabling remote administration features if they are not strictly necessary reduces the attack surface available to external attackers. Security monitoring should also be enhanced to detect unusual POST requests targeting CGI endpoints associated with configuration retrieval functions, which may indicate active exploitation attempts.