CVE-2021-42887 in EX1200T
Summary
by MITRE • 06/03/2022
In TOTOLINK EX1200T V4.1.2cu.5215, an attacker can bypass login by sending a specific request through formLoginAuth.htm.
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Analysis
by VulDB Data Team • 06/08/2022
The vulnerability identified as CVE-2021-42887 affects the TOTOLINK EX1200T router model running firmware version V4.1.2cu.5215, representing a critical authentication bypass flaw that compromises the device's security posture. This issue resides within the web-based management interface, specifically in the formLoginAuth.htm component which handles user authentication requests. The vulnerability allows an unauthenticated attacker to gain administrative access to the router without proper credentials, fundamentally undermining the device's access control mechanisms. Such a flaw represents a severe weakness in the router's security architecture, as it eliminates the primary barrier that should prevent unauthorized individuals from accessing sensitive network configuration parameters and management functions.
The technical implementation of this vulnerability stems from insufficient input validation and authentication checks within the login authentication handler. When an attacker sends a specifically crafted request to the formLoginAuth.htm endpoint, the system fails to properly verify the authentication state or validate the request parameters before granting access privileges. This weakness likely originates from improper session management or flawed authentication token handling within the router's web server implementation. The vulnerability falls under CWE-287 which specifically addresses improper authentication issues, and more broadly aligns with CWE-305 which deals with authentication bypass through multiple means. From an operational perspective, this vulnerability creates a direct pathway for attackers to execute the techniques outlined in the MITRE ATT&CK framework under T1078 which covers valid accounts and T1566 which encompasses credential harvesting and manipulation.
The operational impact of CVE-2021-42887 extends far beyond simple unauthorized access, as it enables attackers to assume complete administrative control over the affected router. This level of access allows adversaries to modify network configurations, install malicious firmware, redirect traffic through malicious proxies, or establish backdoors for persistent access. The compromised router can then serve as a pivot point for lateral movement within the network, potentially enabling attackers to access connected devices, internal systems, and sensitive data repositories. Network traffic passing through the compromised device may be intercepted, modified, or monitored, creating a significant risk for data confidentiality and integrity. Additionally, attackers can disable security features such as firewalls, DNS filtering, or intrusion detection systems, leaving the entire network vulnerable to further exploitation. The implications are particularly severe for enterprise environments where these routers may serve as network gateways or provide connectivity for critical business systems.
Mitigation strategies for this vulnerability require immediate firmware updates from TOTOLINK to address the authentication bypass flaw in the web interface. Organizations should implement network segmentation to limit the attack surface and prevent lateral movement if a device is compromised. Network monitoring should be enhanced to detect unusual traffic patterns or unauthorized access attempts to management interfaces. Access controls should be strengthened by disabling unnecessary web management interfaces, implementing strong authentication mechanisms, and restricting access to management functions from specific IP addresses or networks. Regular security audits and vulnerability assessments should be conducted to identify similar weaknesses in network infrastructure devices. From a defense-in-depth perspective, implementing network access control lists, intrusion detection systems, and monitoring for unauthorized administrative access attempts can help detect and prevent exploitation of this vulnerability. Organizations should also consider implementing multi-factor authentication for administrative access where possible and maintain up-to-date inventories of all network devices to ensure comprehensive vulnerability management coverage.