CVE-2004-2146 in MegaBBS
Summary
by MITRE
CRLF injection vulnerability in PD9 Software MegaBBS 2 and 2.1 allows attackers to conduct HTTP response splitting attacks via the fid parameter in a writenew action to thread-post.asp.
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Analysis
by VulDB Data Team • 06/25/2018
The CVE-2004-2146 vulnerability represents a critical security flaw in PD9 Software MegaBBS versions 2 and 2.1 that enables attackers to execute HTTP response splitting attacks through improper input validation. This vulnerability specifically targets the fid parameter within the writenew action of the thread-post.asp script, creating a pathway for malicious actors to manipulate HTTP responses and potentially redirect users to harmful content. The issue stems from insufficient sanitization of user-supplied input that flows directly into HTTP response headers, violating fundamental security principles of input validation and output encoding.
The technical implementation of this vulnerability exploits the inherent characteristics of HTTP response construction where attackers can inject carriage return line feed sequences into the fid parameter to manipulate the response headers. When the vulnerable application processes this parameter without proper sanitization, it allows attackers to inject additional HTTP headers into the response, effectively splitting the response and enabling various attack vectors including cross-site scripting, session hijacking, and cache poisoning. This vulnerability aligns with CWE-113, which specifically addresses improper neutralization of CRLF characters in HTTP headers, and represents a classic example of HTTP response splitting as defined in the OWASP Top Ten vulnerabilities.
The operational impact of this vulnerability extends beyond simple data manipulation, as it provides attackers with the capability to redirect users to malicious websites, inject malicious content into web pages, or even steal session cookies through carefully crafted header injections. Attackers can leverage this vulnerability to perform man-in-the-middle attacks, where they intercept and modify HTTP responses between users and the vulnerable application. The attack surface is particularly concerning given that the vulnerability exists in a bulletin board system where user-generated content is common, making it difficult to distinguish between legitimate and malicious input. This weakness can be exploited through various methods including web application attacks, social engineering, or by leveraging other vulnerabilities in the application stack to establish persistent access.
Mitigation strategies for CVE-2004-2146 must focus on implementing robust input validation and output encoding mechanisms throughout the application's request handling process. The most effective approach involves sanitizing all user-supplied input, particularly parameters that flow into HTTP response headers, using strict validation patterns that reject or encode CRLF characters. Organizations should implement proper parameter validation routines that ensure the fid parameter conforms to expected formats and ranges, while also applying output encoding techniques to prevent header injection attacks. Additionally, web application firewalls and security monitoring systems should be configured to detect and block suspicious header injection patterns. The remediation process requires comprehensive code review to identify all input parameters that could potentially affect HTTP responses, and implementing consistent security controls across all application components to prevent similar vulnerabilities from emerging in other areas of the system. This vulnerability demonstrates the critical importance of following secure coding practices and adheres to ATT&CK technique T1566, which covers credential access through application vulnerabilities, and T1071, which addresses application layer protocol usage for command and control communications.