CVE-2026-51617 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getSysStatusCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain sensitive information such as operation mode, firmware version, serial number, WAN/LAN IP addresses, WiFi SSID, encryption keys, and connected client statistics 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 versions 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 getSysStatusCfg function, which is invoked when processing requests directed to the /cgi-bin/cstecgi.cgi endpoint. This architectural weakness allows unauthenticated actors to bypass standard authentication requirements and retrieve sensitive system configuration data. The absence of proper authorization checks means that any external or internal network user can interact with this administrative interface without providing valid credentials, effectively treating a privileged operation as if it were public-facing.
The technical nature of this flaw is classified under CWE-284, which denotes Improper Access Control. By exploiting the misconfigured endpoint, an attacker can send crafted POST requests to retrieve detailed system status information. The data exposed includes operational mode, specific firmware versioning details, unique hardware identifiers such as serial numbers, and network configuration specifics like WAN and LAN IP addresses. Furthermore, the vulnerability extends to highly sensitive cryptographic material, including WiFi SSID names and encryption keys used for securing wireless communications. Additionally, connected client statistics are disclosed, revealing information about devices currently associated with the local network. This level of detail provides a comprehensive map of the target environment, facilitating further reconnaissance efforts.
From an operational impact perspective, this vulnerability significantly lowers the barrier for subsequent attacks against the router and the broader network it secures. The disclosure of encryption keys allows attackers to decrypt wireless traffic or impersonate legitimate access points in man-in-the-middle scenarios. Knowledge of connected client statistics enables targeted phishing or exploitation of specific devices on the local area network. Exposure of firmware versions aids in identifying known vulnerabilities associated with that specific build, while serial numbers and IP addresses assist in mapping the physical location and identity of the victim for more sophisticated social engineering or supply chain attacks. This aligns with ATT&CK technique T1087, which covers Account Discovery on local systems, as well as T1592, Gather Victim Host Information, indicating that this flaw serves as a primary entry point for deeper network infiltration.
Mitigation strategies must focus on immediate remediation and long-term security hardening. The most effective solution is to apply the firmware update provided by TOTOLINK that patches the access control logic in the getSysStatusCfg function. Until an official patch is available, administrators should restrict access to the management interface /cgi-bin/cstecgi.cgi using firewall rules or network segmentation policies, ensuring it is only reachable from trusted internal subnets rather than exposed to untrusted networks like the WAN side. Additionally, changing default credentials and disabling remote administration features can reduce the attack surface. Regular security audits of embedded web interfaces are recommended to detect similar misconfigurations in other functions that may inadvertently expose sensitive system states without proper authentication checks.