CVE-2026-51709 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the setWiFiBasicCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to reconfigure primary Wi-Fi settings 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 setWiFiBasicCfg function, which is responsible for configuring primary Wi-Fi parameters such as SSID, security type, and encryption keys. This component fails to enforce proper authentication checks before processing configuration changes initiated by users or external entities. As a result, any individual with network access to the router can manipulate these settings without providing valid administrative credentials. The attack vector involves sending a crafted HTTP POST request directly to the /cgi-bin/cstecgi.cgi endpoint, bypassing the standard login portal entirely. This type of vulnerability is commonly classified under CWE-269 Improper Privilege Assignment or CWE-862 Missing Authorization, highlighting the fundamental breakdown in verifying user permissions before executing sensitive operations.
From an operational perspective, this flaw allows unauthenticated attackers to take full control over the wireless network configuration. An attacker can change the Wi-Fi name and password, effectively locking out legitimate users while gaining exclusive access to the local area network. Furthermore, by altering security settings, such as disabling encryption or switching to open networks, the attacker can expose all connected devices to eavesdropping and man-in-the-middle attacks. This capability also enables the attacker to redirect traffic through malicious DNS servers or inject malware into unencrypted communications flowing between clients and the internet. In enterprise environments, this could lead to lateral movement as compromised endpoints provide a foothold for further intrusion into internal systems. The ability to reconfigure primary Wi-Fi settings without authentication significantly lowers the barrier for entry, making it accessible even to attackers with limited technical expertise who can utilize automated tools or simple scripts to exploit the endpoint.
The exploitation of this vulnerability aligns with several tactics in the MITRE ATT&CK framework. It corresponds primarily to T1078 Valid Accounts if the attacker uses stolen credentials, but more critically, it fits T1546 Event Triggered Execution and potentially T1136 Local Account Creation depending on how the configuration is abused. However, since no authentication is required, it most closely resembles unauthorized access patterns seen in privilege escalation or direct exploitation of misconfigured services. The persistence gained through this vulnerability allows attackers to maintain long-term access by ensuring they always control the network entry point. Additionally, if combined with other vulnerabilities such as remote code execution via similar CGI endpoints, the impact could escalate from mere configuration manipulation to complete device compromise and botnet recruitment.
Mitigation strategies for this issue must prioritize immediate patching of the firmware to a version where proper authentication checks are enforced in the setWiFiBasicCfg function. Administrators should verify that all administrative interfaces require strong multi-factor authentication or at least robust password policies before allowing any configuration changes. Network segmentation is also recommended to limit the blast radius if an attacker gains initial access, ensuring that compromised IoT devices cannot easily reach critical internal assets. For organizations unable to patch immediately due to operational constraints, implementing strict firewall rules to restrict access to the management interface only from trusted IP addresses can provide a temporary layer of defense. Regular vulnerability scanning and monitoring for unusual HTTP POST requests to CGI endpoints can also aid in early detection of exploitation attempts. Ultimately, vendors must adopt secure coding practices that validate user identity and permissions at every step of request processing to prevent such authorization bypasses in future releases.