CVE-2026-51700 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the setWiFiAdvancedCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to degrade wireless behavior 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 setWiFiAdvancedCfg 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 actors to interact with administrative configuration endpoints that should be restricted to authorized users only. By exploiting this misconfiguration, an attacker can send crafted POST requests to the /cgi-bin/cstecgi.cgi interface without needing valid credentials or session tokens. The absence of proper authentication checks at this specific function level allows external entities to modify critical wireless network parameters directly through HTTP traffic, bypassing standard security gateways that typically enforce user identity verification before allowing configuration changes.
The technical nature of this flaw lies in the server-side processing logic which fails to validate the source or privilege level of the incoming request targeting the setWiFiAdvancedCfg endpoint. In a secure implementation, any attempt to modify advanced wireless settings such as channel selection, transmission power, encryption protocols, or SSID broadcasting would require prior authentication and authorization checks against an active administrative session. Instead, the vulnerable firmware processes these requests blindly, treating them as legitimate commands from an administrator. This lack of input validation regarding user context enables remote attackers to manipulate the device's operational state without detection by standard security monitoring tools that rely on successful login events for anomaly detection.
The operational impact of this vulnerability is significant, primarily centering on the degradation and potential disruption of wireless network services. An attacker can deliberately alter advanced WiFi configurations to degrade performance or cause instability. For instance, they might switch the device to a congested channel with poor signal quality, disable essential security protocols like WPA2/WPA3 encryption leaving the network open to eavesdropping, or reduce transmission power to create dead zones within the coverage area. Such actions effectively result in a denial of service for legitimate users who rely on stable and secure wireless connectivity. Furthermore, by weakening security settings, the attacker may facilitate further attacks such as man-in-the-middle interceptions or unauthorized access to devices connected to the compromised network, thereby expanding the scope of potential damage beyond mere inconvenience to serious data privacy breaches.
From a threat intelligence perspective, this vulnerability aligns with ATT&CK technique T1548 Abuse Elevation Control Mechanism and potentially T1078 Valid Accounts if combined with credential stuffing, although in this specific case it is exploited without valid accounts due to the access control flaw. The ability to modify system configuration remotely via web interface exploits places this vulnerability within the context of remote code execution or service manipulation vectors commonly seen in IoT device compromises. Attackers can leverage this weakness as an initial foothold to pivot into internal networks, especially if the router serves as a gateway for sensitive corporate or home network segments where lateral movement is possible once basic connectivity controls are manipulated.
Mitigation strategies must prioritize immediate patching of the firmware to version 4.1.5cu.748_B20211016 or later, assuming the vendor has addressed this specific access control oversight in subsequent releases. If updating is not immediately feasible, network administrators should implement strict firewall rules that restrict access to /cgi-bin/cstecgi.cgi exclusively from trusted management IP addresses and disable remote administration features entirely if they are not required for legitimate operations. Additionally, deploying intrusion detection systems configured to monitor for unusual POST requests targeting CGI endpoints can help in detecting exploitation attempts in real-time. Long-term remediation involves enforcing the principle of least privilege across all firmware components and conducting rigorous security audits that include automated testing for broken access control vulnerabilities before deployment.