CVE-2004-2054 in phpBB
Summary
by MITRE
CRLF injection vulnerability in PhpBB 2.0.4 and 2.0.9 allows remote attackers to perform HTTP Response Splitting attacks to modify expected HTML content from the server via (1) the mode parameter to privmsg.php or (2) the redirect parameter to login.php.
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Analysis
by VulDB Data Team • 07/06/2025
The CVE-2004-2054 vulnerability represents a critical CRLF injection flaw in PhpBB versions 2.0.4 and 2.0.9 that enables remote attackers to execute HTTP response splitting attacks. This vulnerability stems from inadequate input validation mechanisms within the web application's parameter processing logic, specifically affecting two distinct endpoints: the mode parameter in privmsg.php and the redirect parameter in login.php. The flaw operates by allowing malicious actors to inject carriage return line feed sequences into HTTP response headers, thereby manipulating the server's response structure and potentially redirecting user traffic to malicious destinations. This vulnerability directly maps to CWE-113, which describes improper neutralization of CRLF characters in HTTP headers, and aligns with ATT&CK technique T1190 for exploitation of vulnerabilities in web applications. The security implications extend beyond simple content modification, as response splitting can enable more sophisticated attacks including session hijacking, cross-site scripting, and cache poisoning.
The technical exploitation of this vulnerability occurs when user-supplied input containing CRLF sequences is directly incorporated into HTTP response headers without proper sanitization or encoding. When attackers manipulate the mode parameter in privmsg.php or the redirect parameter in login.php, they can inject malicious header content that causes the web server to send multiple HTTP responses instead of a single intended response. This creates a condition where the browser receives multiple responses, potentially allowing attackers to inject malicious content or redirect users to phishing sites. The vulnerability demonstrates a classic lack of proper input validation and output encoding practices that are fundamental to secure web application development. Attackers can leverage this flaw to inject arbitrary HTTP headers, manipulate cookies, or redirect users to malicious websites while maintaining the appearance of legitimate server responses.
The operational impact of CVE-2004-2054 extends significantly beyond immediate content manipulation, as it provides attackers with a foothold for more comprehensive attacks against PhpBB installations. Organizations running affected versions face potential data breaches, session hijacking, and user redirection attacks that can compromise user privacy and system integrity. The vulnerability affects the core authentication and messaging functionality of PhpBB, potentially allowing attackers to intercept user credentials, manipulate private messages, or gain unauthorized access to user accounts. Security professionals must recognize that this vulnerability can be exploited in combination with other attack vectors, creating opportunities for more sophisticated breaches. The impact is particularly severe given that PhpBB was widely deployed for forum hosting, meaning that successful exploitation could affect numerous websites simultaneously. This vulnerability highlights the importance of proper input validation and the principle of least privilege in web application security architecture.
Mitigation strategies for CVE-2004-2054 require immediate implementation of input sanitization measures and proper HTTP header encoding practices. Organizations should upgrade to patched versions of PhpBB as soon as possible, as this vulnerability was addressed in subsequent releases. The recommended remediation includes implementing strict validation of all user-supplied input parameters, particularly those used in HTTP header construction. Security measures should enforce proper encoding of special characters including carriage return and line feed sequences before incorporating user data into HTTP responses. Organizations should also implement web application firewalls and input validation rules that can detect and block CRLF injection attempts. Additional protective measures include monitoring for unusual header patterns and implementing proper HTTP response handling that prevents header injection attacks. The vulnerability underscores the necessity of following secure coding practices such as those outlined in the OWASP Secure Coding Practices and emphasizes the importance of regular security audits and vulnerability assessments to identify and remediate similar flaws in web applications.