CVE-2004-1996 in SMF
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Simple Machines Forum (SMF) 1.0 allows remote attackers to inject arbitrary web script via the size tag.
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Analysis
by VulDB Data Team • 06/09/2025
The vulnerability identified as CVE-2004-1996 represents a critical cross-site scripting flaw within Simple Machines Forum version 1.0, specifically targeting the forum's handling of the size HTML tag. This weakness enables remote attackers to execute malicious scripts in the context of other users' browsers, potentially compromising user sessions and data integrity. The vulnerability resides in the forum's input sanitization mechanisms, which fail to properly validate or escape user-supplied content containing size tags that could be exploited for malicious purposes.
The technical exploitation of this vulnerability occurs when an attacker crafts malicious content containing a size tag with embedded script code, which is then rendered on forum pages viewed by other users. This particular implementation flaw allows attackers to bypass existing security measures that should normally prevent script execution within forum content. The vulnerability specifically affects the SMF 1.0 version where the forum software fails to adequately sanitize HTML attributes, particularly those related to font size specifications that could contain executable code. This weakness falls under CWE-79 which categorizes improper neutralization of input during web page generation, specifically addressing cross-site scripting vulnerabilities.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform session hijacking, steal sensitive user information, manipulate forum content, or redirect users to malicious websites. Users who view affected forum posts become unwitting participants in the attack, with their browsers executing the injected scripts without their knowledge or consent. This makes the vulnerability particularly dangerous in community forums where users trust the content and may not be aware of the security implications. The attack vector is straightforward and requires minimal technical expertise, making it a popular target for attackers seeking to compromise forum communities.
Organizations and forum administrators should implement immediate mitigations including input validation and output encoding for all user-generated content, particularly HTML attributes related to font sizing. The recommended approach involves sanitizing all HTML tags and attributes before rendering content, ensuring that size attributes cannot contain script code or other executable elements. Additionally, implementing Content Security Policy headers can provide an additional layer of protection against script execution. The vulnerability demonstrates the critical importance of proper input validation and output encoding as outlined in the OWASP Top Ten security principles. Security teams should also consider upgrading to patched versions of SMF where available, as this vulnerability was addressed in subsequent releases through improved HTML sanitization routines. Regular security auditing of forum software and input handling mechanisms remains essential to prevent similar vulnerabilities from emerging in web applications.