CVE-2004-1950 in phpBB
Summary
by MITRE
phpBB 2.0.8a and earlier trusts the IP address that is in the X-Forwarded-For in the HTTP header, which allows remote attackers to spoof IP addresses.
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Analysis
by VulDB Data Team • 06/18/2018
The vulnerability described in CVE-2004-1950 represents a critical security flaw in phpBB versions 2.0.8a and earlier that fundamentally undermines the integrity of user identification and access control mechanisms. This issue stems from the application's improper handling of HTTP headers, specifically the X-Forwarded-For header, which is commonly used in web environments where applications operate behind load balancers, proxies, or firewalls. The flaw occurs because phpBB incorrectly places complete trust in the IP address information provided through this header without proper validation or sanitization, creating a pathway for malicious actors to manipulate the perceived origin of web requests.
The technical implementation of this vulnerability exploits the trust model inherent in the phpBB application's session management and user tracking systems. When a user accesses a phpBB forum, the application typically records the client's IP address for various purposes including security logging, access control, and user identification. However, the vulnerable versions fail to implement proper header validation mechanisms, allowing attackers to inject malicious IP addresses through the X-Forwarded-For header. This header is designed to identify the original IP address of a client connecting to a web server through an HTTP proxy or load balancer, but when improperly handled, it becomes a vector for IP address spoofing attacks. The flaw directly relates to CWE-284, which addresses improper access control, and CWE-20, which covers input validation issues.
The operational impact of this vulnerability extends beyond simple IP address spoofing, potentially enabling attackers to circumvent security measures, manipulate user access controls, and conduct various malicious activities within the forum environment. An attacker could exploit this weakness to appear as if they are accessing the forum from a trusted IP address, potentially bypassing IP-based restrictions, accessing restricted areas, or evading automated security mechanisms. This vulnerability particularly affects environments where phpBB is deployed behind reverse proxies or load balancers, which commonly inject X-Forwarded-For headers into requests. The implications are significant for forum administrators who rely on IP-based security controls and user tracking for maintaining community integrity and preventing abuse.
Security mitigations for this vulnerability require immediate implementation of proper header validation and sanitization mechanisms within the phpBB application. Organizations should ensure that the application validates the X-Forwarded-For header against known trusted proxy IP addresses or implements strict validation that verifies the authenticity of the header content. The recommended approach involves implementing a whitelist of trusted proxy servers and ensuring that only headers from these known sources are considered valid. Additionally, administrators should consider implementing proper input validation for all HTTP headers and ensure that the application does not blindly trust any header values without proper verification. This vulnerability aligns with ATT&CK technique T1566, which covers phishing with malicious attachments, and demonstrates the importance of proper input validation in preventing header injection attacks that can lead to privilege escalation and unauthorized access to web applications. The fix requires updating to phpBB version 2.0.9 or later, which implements proper header validation mechanisms and addresses the trust model issue inherent in earlier versions.