CVE-2026-51633 in TOTOLINK
Summary
by MITRE • 08/28/2026
Incorrect access control in the getWiFiEasyGuestCfg function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to obtain simplified guest Wi-Fi configuration, including guest credentials, 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 getWiFiEasyGuestCfg function, which is designed to retrieve configuration details for guest Wi-Fi networks. Under normal operational parameters, this endpoint should require valid administrative authentication credentials before returning sensitive data. However, due to an implementation error, the system fails to enforce these security controls effectively. This allows unauthenticated attackers who have network access to the router's management interface to bypass authorization checks entirely. By sending a specifically crafted POST request to the /cgi-bin/cstecgi.cgi endpoint, external actors can trigger this function without providing any valid session tokens or login credentials.
The technical nature of this flaw is classified as an improper privilege check or broken access control issue. The server-side logic processes requests for guest configuration data regardless of whether the requester has been authenticated as a privileged user. This lack of verification means that any entity capable of reaching the router's IP address on the management port can exploit this weakness. The attack vector involves constructing an HTTP POST request with specific parameters that target the getWiFiEasyGuestCfg function. Because the server does not validate the source or authentication status before executing the query, it proceeds to fetch and return the requested configuration data directly in the response payload. This behavior violates fundamental security principles regarding the protection of sensitive system information from unauthorized parties.
The operational impact of this vulnerability is significant for users relying on TOTOLINK routers for secure network segmentation. Guest Wi-Fi configurations typically contain credentials such as SSID names, encryption keys (WPA2/WPA3 passphrases), and potentially other settings that define how guest devices connect to the network. The exposure of these details allows attackers to gain unauthorized access to the guest wireless network. While guest networks are often isolated from the main local area network for security reasons, gaining entry still poses risks including bandwidth theft, illegal activities attributed to the primary user, and potential lateral movement if isolation mechanisms are misconfigured or flawed. Furthermore, knowledge of the router's configuration can aid in further reconnaissance, allowing attackers to identify other vulnerabilities or tailor attacks against connected devices within that segment.
This vulnerability aligns with CWE-284, which describes Improper Access Control, where a system fails to restrict access to resources for unauthorized actors. In terms of offensive security frameworks, this exploitation technique maps to the ATT&CK tactic of Initial Access and specifically relates to techniques involving exploiting misconfigurations in web applications or services. The ability to retrieve sensitive configuration data without authentication also touches upon CWE-200, which covers Exposure of Sensitive Information to an Unauthorized Actor. Such exposures undermine the confidentiality integrity of the network infrastructure and can lead to broader security compromises if not addressed promptly.
Mitigation strategies for this vulnerability primarily involve updating the router firmware to a patched version where the access control checks have been corrected in the getWiFiEasyGuestCfg function. Administrators should verify their current firmware version against vendor release notes to determine if an update is available. In cases where immediate patching is not feasible, temporary mitigations include restricting management interface access through firewall rules or VLAN segmentation so that only trusted administrative workstations can reach the router's CGI endpoints. Additionally, changing default credentials and ensuring strong password policies for any remaining accessible services reduces the attack surface, although this specific flaw does not rely on weak passwords but rather a logic error in authentication enforcement. Regular security audits and penetration testing of network infrastructure components are recommended to identify similar access control deficiencies before they can be exploited by malicious actors.