CVE-2004-2157 in Serendipity
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Comment.php in Serendipity 0.7 beta1, and possibly other versions before 0.7-beta3, allows remote attackers to inject arbitrary HTML and PHP code via the (1) email or (2) username field.
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Analysis
by VulDB Data Team • 07/06/2025
The vulnerability identified as CVE-2004-2157 represents a critical cross-site scripting flaw discovered in the Serendipity blog publishing platform version 0.7 beta1 and potentially affecting earlier versions up to 0.7-beta3. This vulnerability resides within the Comment.php component of the application, which handles user comments submitted to blog entries. The flaw manifests when the application fails to properly sanitize user input before rendering it within the web page context, creating an avenue for malicious actors to inject harmful code into the comment submission process.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding mechanisms within the comment handling system. Attackers can exploit this weakness by submitting specially crafted payloads through either the email or username fields during comment submission. When these fields contain malicious code, the application processes the input without adequate sanitization, allowing the injected HTML and PHP code to execute within the context of other users' browsers. This particular vulnerability maps directly to CWE-79, which defines Cross-site Scripting as a weakness where untrusted data is sent to a web browser without proper validation or encoding, enabling attackers to execute scripts in the victim's browser context.
The operational impact of this vulnerability extends beyond simple data theft or defacement, as it enables attackers to establish persistent malicious presence within the affected blog environment. An attacker could inject scripts that steal session cookies, redirect users to malicious sites, or even modify content displayed to other visitors. The vulnerability's exploitation requires minimal technical skill and can be automated, making it particularly dangerous for widespread deployment. Given that comment sections are frequently accessed and often contain user-generated content, this flaw provides attackers with a readily available vector for delivering malicious payloads to unsuspecting visitors. The vulnerability also aligns with ATT&CK technique T1566, which covers the use of social engineering through malicious content delivery, specifically targeting web applications through user interaction with compromised content.
Mitigation strategies for CVE-2004-2157 should prioritize immediate application updates to version 0.7-beta3 or later, where the vulnerability has been addressed through proper input sanitization and output encoding. Organizations should implement comprehensive input validation at multiple levels, ensuring that all user-supplied data undergoes strict sanitization before being stored or rendered in web pages. This includes implementing proper HTML escaping techniques for all dynamic content and establishing Content Security Policy headers to limit script execution capabilities. Additionally, administrators should consider implementing web application firewalls that can detect and block suspicious input patterns commonly associated with XSS attacks, while maintaining regular security audits of web applications to identify similar vulnerabilities that may exist in other components of the system.