CVE-2026-51698 in TOTOLINK
Summary
by MITRE • 08/31/2026
Incorrect access control in the setUrlFilterRules function of TOTOLINK T6 4.1.5cu.748_B20211015 allows unauthenticated attackers to alter browsing policies 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 setUrlFilterRules function of TOTOLINK T6 router 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 attackers to manipulate browsing policies by transmitting crafted POST requests to the /cgi-bin/cstecgi.cgi endpoint. In typical router architectures, functions responsible for modifying administrative settings such as URL filtering rules should require valid authentication credentials and session tokens to ensure that only authorized users can alter system configurations. The absence of these checks in this specific function creates a direct path for unauthorized modification of network security policies.
From an operational perspective, the ability to alter browsing policies without authentication allows attackers to bypass content restrictions designed to protect users from malicious or inappropriate websites. This could involve disabling parental controls, removing blocks on known malware distribution sites, or redirecting traffic through attacker-controlled domains via DNS manipulation if such features are linked to URL filtering rules. The impact extends beyond simple policy changes; it undermines the integrity of the router as a security boundary between the internal network and the internet. Attackers can effectively neutralize one layer of defense, making connected devices more susceptible to phishing attacks, drive-by downloads, and other web-based threats that rely on user interaction with compromised or malicious content.
This vulnerability aligns closely with ATT&CK technique T1562.001 Impair Defenses: Disable or Modify Tools, as it involves the modification of security tools (in this case, URL filtering rules) to reduce their effectiveness. Furthermore, because the attack vector is remote and requires no prior authentication, it falls under Remote Code Execution principles where configuration changes are executed without proper authorization checks, often categorized under CWE-862 Missing Authorization in broader contexts of web application vulnerabilities. The exploitation likely involves crafting a specific HTTP POST request with parameters that trigger the setUrlFilterRules function while omitting or bypassing expected authentication headers or tokens, exploiting the server-side logic flaw directly through standard network interfaces.
Mitigation strategies for this vulnerability primarily involve immediate firmware updates provided by TOTOLINK to patch the access control checks within the cstecgi.cgi script. Administrators should verify their current firmware version and apply any available patches that address improper authorization in administrative functions. In environments where updating is not immediately feasible, temporary mitigations include restricting access to the router's management interface through network segmentation or firewall rules, ensuring that only trusted IP addresses can reach the /cgi-bin/ endpoints. Additionally, enabling strong authentication mechanisms if supported by older firmware versions and monitoring logs for unusual POST requests to administrative CGI scripts can help detect potential exploitation attempts before significant damage occurs.