CVE-2009-3287 in thin
Summary
by MITRE
lib/thin/connection.rb in Thin web server before 1.2.4 relies on the X-Forwarded-For header to determine the IP address of the client, which allows remote attackers to spoof the IP address and hide activities via a modified X-Forwarded-For header.
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Analysis
by VulDB Data Team • 01/20/2019
The vulnerability identified as CVE-2009-3287 affects the Thin web server version 1.2.3 and earlier, specifically within the lib/thin/connection.rb file. This represents a critical security flaw that stems from the server's improper handling of client IP address identification mechanisms. The Thin web server, a popular Ruby-based HTTP server, implements a default configuration that trusts the X-Forwarded-For header for determining client IP addresses without proper validation or sanitization. This design decision creates a fundamental security weakness that directly violates secure coding principles and industry best practices for input validation.
The technical flaw manifests when the Thin web server processes incoming HTTP requests and encounters an X-Forwarded-For header. Instead of implementing proper validation mechanisms or employing additional security checks, the server blindly accepts and trusts the IP address values provided in this header. The X-Forwarded-For header is a de facto standard HTTP header used by proxies and load balancers to identify the original client IP address when requests pass through multiple network hops. However, this header can be easily manipulated by malicious actors who have access to the network path or can intercept traffic. Attackers can craft malicious X-Forwarded-For headers containing arbitrary IP addresses, allowing them to completely mask their true network location and appear as if they are connecting from different systems. This vulnerability directly maps to CWE-284 Access Control and CWE-352 Cross-Site Request Forgery categories, as it enables attackers to bypass access controls and conceal their activities.
The operational impact of this vulnerability is significant and multifaceted. Remote attackers can exploit this weakness to conduct various malicious activities including but not limited to IP-based access control bypass, denial of service attacks, and unauthorized access attempts. The ability to spoof IP addresses undermines the integrity of any security measures that rely on client IP identification for logging, monitoring, or access control decisions. Security administrators lose visibility into actual client locations, making forensic analysis and incident response extremely difficult. Attackers can also leverage this vulnerability to circumvent IP-based rate limiting, authentication mechanisms, and other network-level security controls that depend on accurate IP address determination. This vulnerability creates a false sense of security for administrators who may rely on IP address logging for threat detection and analysis, potentially allowing malicious activities to go undetected for extended periods.
The mitigation strategy for this vulnerability requires immediate action to upgrade to Thin web server version 1.2.4 or later, which contains the necessary patches to address the IP address validation issue. Organizations should also implement additional security measures such as configuring reverse proxies with proper header validation, implementing network-level access controls, and establishing robust logging mechanisms that can detect anomalous IP address patterns. Security teams must review their current monitoring and alerting systems to ensure they can identify suspicious X-Forwarded-For header values. Network administrators should consider implementing strict header validation policies at the proxy or load balancer level, ensuring that only trusted upstream proxies can modify or provide X-Forwarded-For headers. The ATT&CK framework categorizes this vulnerability under T1566 Credential Access and T1071 Application Layer Protocol, as it enables attackers to manipulate application layer headers to bypass security controls. Regular security audits should include verification of header handling mechanisms and proper input validation across all web applications and servers to prevent similar vulnerabilities from being introduced in future implementations.