CVE-2026-51652 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getUPnPCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain UPnP enablement and parsed port-mapping 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 getUPnPCfg function, which is invoked when processing POST requests directed to the /cgi-bin/cstecgi.cgi endpoint. This architectural weakness allows unauthenticated actors to interact with sensitive configuration endpoints that should strictly require administrative privileges or valid session tokens. By exploiting this misconfiguration, an attacker can retrieve detailed information regarding Universal Plug and Play (UPnP) settings without any form of authentication, effectively bypassing the intended security boundaries established by the vendor for managing network address translation and port forwarding rules.
From a technical perspective, the core issue is classified as CWE-284, Improper Access Control, where the application fails to enforce proper authorization checks before executing sensitive operations. The getUPnPCfg function processes incoming HTTP POST requests but does not adequately verify the identity or privilege level of the requester. This oversight enables remote unauthenticated attackers to send crafted payloads that trigger the retrieval of UPnP configuration data. The response typically includes whether UPnP is enabled on the device and provides parsed details about existing port mappings, such as internal IP addresses, external ports, and protocol types. This information disclosure occurs over standard HTTP traffic, making it easily exploitable by any entity with network connectivity to the router's management interface, including potential remote attackers if the web interface is exposed to the internet or compromised local networks.
The operational impact of this vulnerability extends beyond simple data leakage. UPnP configuration details are instrumental for an attacker seeking to map internal network topology and identify active services running on connected devices. With knowledge of enabled port mappings, an adversary can pinpoint specific applications that have opened inbound connections through the router's firewall. This intelligence facilitates further attacks such as direct exploitation of vulnerable services, lateral movement within the local area network, or even setting up persistent backdoors by modifying existing rules if write access were also compromised. The exposure of UPnP status indicates whether the device is actively allowing automatic port forwarding requests from internal clients, which significantly increases the attack surface for malware that relies on UPnP to establish command-and-control channels without manual user intervention.
This vulnerability aligns with several entries in the MITRE ATT&CK framework, particularly T1046 Network Service Discovery and T1592 Gather Victim Host Information. The ability to enumerate network services via port mapping data supports reconnaissance phases of an attack chain, allowing adversaries to build a detailed map of the target environment before launching more intrusive exploits. Furthermore, it relates to CWE-200 Exposure of Sensitive Information to an Unauthorized Actor, highlighting how improper access controls lead directly to information disclosure that aids subsequent malicious activities. The lack of authentication for this specific CGI endpoint underscores a broader trend in embedded device security where convenience often overrides rigorous access control implementation during development and testing phases.
Mitigation strategies must prioritize immediate patching if the vendor has released an updated firmware version addressing this access control flaw. In environments where updating is not immediately feasible, network segmentation should be employed to restrict access to the router's management interface exclusively from trusted administrative subnets. Additionally, disabling UPnP functionality entirely through alternative configuration methods or physical reset procedures can eliminate the attack vector associated with port mapping enumeration. Security teams should also implement strict ingress filtering and web application firewalls that monitor for anomalous POST requests targeting CGI endpoints lacking proper session validation. Regular audits of embedded device configurations against industry standards such as CWE-284 are essential to prevent similar access control failures in other network infrastructure components.