CVE-2026-51686 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the setWiFiEasyCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to reconfigure or disable wireless networks 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 device's web management interface. Specifically, the flaw resides in the setWiFiEasyCfg function, which is designed to handle configuration changes for wireless networks using Wi-Fi Easy Config protocols. This component fails to properly validate whether the incoming request originates from an authenticated administrator or allows unauthenticated actors to execute administrative functions. By exploiting this misconfiguration, attackers can send crafted POST requests directly to the /cgi-bin/cstecgi.cgi endpoint without requiring valid credentials, effectively bypassing authentication controls that should restrict such operations to authorized users only.
From a technical perspective, this vulnerability is classified under CWE-269, which denotes Improper Privilege Assignment or Incorrect Access Control. The root cause lies in the server-side logic of the Common Gateway Interface script responsible for processing Wi-Fi configuration updates. Instead of verifying session tokens, cookies, or other authentication markers before executing sensitive commands like disabling wireless interfaces or altering network parameters, the application blindly processes requests directed at this specific endpoint. This lack of authorization checks allows remote attackers to manipulate the router's state arbitrarily. The ability to reconfigure or disable wireless networks remotely means that an attacker can disrupt local connectivity for all users on the network, potentially causing a denial of service condition for legitimate clients while simultaneously gaining control over the device's radio settings.
The operational impact of this vulnerability is significant for both residential and small business environments relying on TOTOLINK routers. An unauthenticated remote attacker located anywhere with network access to the router can exploit this flaw to disable Wi-Fi services, effectively cutting off wireless connectivity for all connected devices. Furthermore, the ability to reconfigure these networks may allow an attacker to change SSIDs or security settings, potentially facilitating further attacks such as evil twin AP setups or redirecting traffic through malicious gateways if combined with other vulnerabilities like DNS hijacking. This level of control undermines the integrity and availability of the network infrastructure, compromising user trust and operational continuity.
In terms of threat modeling, this vulnerability aligns with MITRE ATT&CK techniques related to Initial Access and Persistence via compromised devices. Specifically, it relates to T1505.003 Server Software Component: Web Shell or similar administrative interface exploitation where attackers leverage misconfigured web applications to gain footholds. The attack vector is remote and requires no user interaction beyond the attacker sending a network packet, making it highly scalable for automated scanning tools targeting vulnerable IoT devices on public IP addresses.
To mitigate this risk, users of TOTOLINK T6 routers running firmware version 4.1.5cu.748_B20211015 or potentially other affected versions should immediately check for and install any available firmware updates provided by the manufacturer that address access control flaws in the web interface. If no update is currently available, administrators can implement network-level mitigations such as restricting management port access to trusted IP addresses via firewall rules or disabling remote administration features entirely if not required. Additionally, changing default administrative passwords and ensuring strong authentication policies remain essential baseline security practices, although they do not directly fix this specific code-level flaw in the setWiFiEasyCfg function. Monitoring for unusual network activity or unauthorized configuration changes can also help detect exploitation attempts early.