CVE-2004-1620 in Serendipity
Summary
by MITRE
CRLF injection vulnerability in Serendipity before 0.7rc1 allows remote attackers to perform HTTP Response Splitting attacks to modify expected HTML content from the server via the url parameter in (1) index.php and (2) exit.php, or (3) the HTTP Referer field in comment.php.
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Analysis
by VulDB Data Team • 06/08/2025
The CVE-2004-1620 vulnerability represents a critical CRLF injection flaw in the Serendipity blogging platform prior to version 0.7rc1, which enables remote attackers to execute HTTP response splitting attacks. This vulnerability operates by exploiting the improper handling of user-supplied input in HTTP headers and URL parameters, creating a pathway for malicious actors to manipulate server responses and inject arbitrary content. The flaw specifically affects three key entry points within the application where user input is directly incorporated into HTTP response headers without adequate sanitization or validation mechanisms.
The technical implementation of this vulnerability stems from the application's failure to properly sanitize input data before incorporating it into HTTP response headers. When users provide input through the url parameter in index.php and exit.php, or through the HTTP Referer field in comment.php, the system processes these values without filtering out carriage return and line feed characters that could be used to inject additional HTTP headers. This CRLF injection allows attackers to insert malicious headers that can redirect users to phishing sites, inject malicious JavaScript, or manipulate the content delivered to users, effectively compromising the integrity of the web application's response handling mechanisms.
The operational impact of this vulnerability extends beyond simple content manipulation, as HTTP response splitting attacks can be leveraged to perform more sophisticated attacks including cross-site scripting exploitation, session hijacking, and cache poisoning. Attackers can craft malicious URLs that, when processed by the vulnerable Serendipity application, create multiple HTTP responses that appear to be legitimate but contain injected content. This vulnerability aligns with CWE-113, which specifically addresses improper neutralization of CRLF characters in HTTP headers, and represents a classic example of how insecure input handling can lead to serious security breaches in web applications. The attack vector demonstrates how seemingly benign user input can be weaponized to compromise the entire application's response integrity.
Mitigation strategies for CVE-2004-1620 require immediate implementation of input validation and sanitization measures across all user-supplied data handling points within the Serendipity platform. Organizations should implement strict filtering of CRLF characters from HTTP headers and URL parameters, ensuring that all user input undergoes proper sanitization before being incorporated into HTTP responses. The recommended solution involves upgrading to Serendipity version 0.7rc1 or later, which includes proper input validation mechanisms to prevent CRLF injection attacks. Additionally, implementing proper header validation and using secure coding practices that prevent direct user input incorporation into HTTP response headers aligns with ATT&CK technique T1071.004 for application layer protocol manipulation. Security teams should also consider implementing web application firewalls that can detect and block CRLF injection attempts, while establishing monitoring procedures to identify potential exploitation attempts. The vulnerability highlights the importance of adhering to secure coding standards and demonstrates how basic input validation can prevent complex attack chains that could otherwise compromise entire web applications.