CVE-2018-5999 in AsusWRT
Summary
by MITRE
An issue was discovered in AsusWRT before 3.0.0.4.384_10007. In the handle_request function in router/httpd/httpd.c, processing of POST requests continues even if authentication fails.
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Analysis
by VulDB Data Team • 08/04/2024
The vulnerability identified as CVE-2018-5999 represents a critical authentication bypass flaw in AsusWRT firmware versions prior to 3.0.0.4.384_10007. This issue resides within the router's web server implementation and specifically affects the handle_request function located in router/httpd/httpd.c. The flaw demonstrates a fundamental failure in the authentication mechanism that allows unauthorized users to continue processing POST requests even when their authentication credentials have been rejected. This represents a classic example of improper input validation and access control implementation that violates security best practices. The vulnerability creates a pathway for attackers to bypass authentication mechanisms and potentially execute malicious actions on network devices.
The technical implementation of this flaw stems from the improper handling of HTTP request processing flow within the web server component of the router firmware. When a POST request is received, the system should validate authentication credentials before proceeding with request processing. However, the vulnerable code continues to process the request regardless of authentication status, effectively rendering the authentication mechanism ineffective. This behavior creates a condition where unauthorized access can be achieved through simple request manipulation without proper credential verification. The vulnerability falls under CWE-285, which addresses improper authorization issues in software implementations, and specifically relates to CWE-305, which deals with authentication bypass through multiple attempts or flawed authentication logic. The flawed code structure suggests a lack of proper state management and request flow control that should be implemented in secure web server applications.
The operational impact of CVE-2018-5999 extends beyond simple unauthorized access to encompass potential complete system compromise of affected routers. Attackers could leverage this vulnerability to modify router configurations, redirect traffic, install malicious firmware, or establish persistent backdoors within the network infrastructure. Since many users operate routers with default credentials or weak authentication, this vulnerability presents an attractive target for automated exploitation campaigns. The risk is particularly elevated in enterprise environments where routers serve as critical network gateways, as compromised devices could provide attackers with privileged access to internal networks. This vulnerability aligns with ATT&CK technique T1072, which describes the use of application or system exploitation to gain access to network devices, and T1059, which covers command and scripting interpreters for persistence and execution. Network administrators face the challenge of securing devices that may be unknowingly compromised, potentially allowing attackers to monitor network traffic, redirect requests, or create unauthorized access points.
Mitigation strategies for CVE-2018-5999 require immediate firmware updates to versions 3.0.0.4.384_10007 or later, which address the authentication bypass issue through proper request flow control. Organizations should conduct comprehensive inventory assessments to identify all affected devices and prioritize remediation efforts based on network criticality and exposure. Network segmentation and access control measures can provide additional defense in depth, limiting the potential impact of compromised devices. Regular security audits of network infrastructure should include verification of firmware versions and authentication mechanisms. System administrators should implement monitoring for unusual router activity patterns that might indicate exploitation attempts. The vulnerability highlights the importance of proper authentication flow implementation and reinforces the need for security testing of network device firmware, particularly in critical infrastructure environments. Organizations should also consider implementing network access control lists and firewall rules to limit external access to router management interfaces, reducing the attack surface for such authentication bypass vulnerabilities.