CVE-2026-51727 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the SystemSettings function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to retrieve administrative import and export endpoint information 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 TOTOLINK T6 router firmware version 4.1.5cu.748_B20211015 represents a critical failure in access control mechanisms within the SystemSettings function of the device's web management interface. This flaw specifically affects the administrative import and export endpoints, which are designed to handle configuration data for backup or migration purposes. Under normal operational conditions, these functions should require valid authentication credentials from an administrator before allowing any interaction with sensitive system configurations. However, due to improper validation checks within the CGI script located at /cgi-bin/cstecgi.cgi, the device fails to enforce this security boundary effectively.
An unauthenticated attacker can exploit this misconfiguration by sending a specifically crafted POST request directly to the affected endpoint without providing valid session tokens or login credentials. The server processes these requests as if they originated from an authenticated administrator, thereby granting unauthorized access to sensitive configuration data. This capability allows external actors to retrieve detailed information about the router's current settings, including network configurations, security policies, and potentially stored credentials embedded within the exported files. Such exposure significantly compromises the confidentiality of the system environment.
From a technical perspective, this issue aligns with CWE-284, which describes Improper Access Control vulnerabilities where authorization checks are either missing or incorrectly implemented. The attack vector is classified under ATT&CK technique T1505.003, known as Web Shell: Server-Side Scripting, although in this specific context it manifests more accurately as unauthorized data exfiltration via API endpoints rather than code execution. The exploitation relies on the attacker's ability to interact with the web interface over HTTP or HTTPS, typically requiring network access to the management port of the router. This could be achieved locally if an adversary has gained foothold within the LAN segment or remotely if the management interface is exposed to the internet without adequate perimeter defenses.
The operational impact of this vulnerability extends beyond simple data leakage. By obtaining administrative configuration files, attackers can analyze the network topology, identify connected devices, and extract hardcoded passwords or API keys that may be present in exported settings. This information serves as a foundation for further attacks, such as privilege escalation, lateral movement within the local network, or even remote code execution if certain configuration parameters allow command injection when re-imported. Furthermore, the ability to export configurations without authentication undermines the integrity of administrative audits and compliance reporting mechanisms that rely on accurate access logs.
Mitigation strategies must prioritize immediate patching by updating the router firmware to a version where this access control flaw has been resolved. In scenarios where updates are not immediately feasible, network segmentation should be enforced to restrict access to the management interface solely from trusted IP addresses or VLANs. Additionally, disabling remote administration features if they are not strictly necessary reduces the attack surface available to external adversaries. Implementing Web Application Firewalls (WAF) with rules targeting suspicious POST requests to CGI endpoints can also provide a layer of defense against exploitation attempts while permanent fixes are deployed. Regular security assessments and penetration testing should be conducted to verify that access controls function as intended across all administrative functions.