CVE-2002-1678 in vBulletin
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in memberlist.php in Jelsoft vBulletin 2.0 rc 2 through 2.2.4 allows remote attackers to steal authentication credentials by injecting script into $letterbits.
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Analysis
by VulDB Data Team • 09/02/2025
The vulnerability identified as CVE-2002-1678 represents a critical cross-site scripting flaw discovered in the memberlist.php script of Jelsoft vBulletin versions 2.0 release candidate 2 through 2.2.4. This vulnerability falls under the CWE-79 category of Cross-Site Scripting and operates by allowing remote attackers to inject malicious scripts into the $letterbits parameter, which is then executed in the context of other users' browsers. The flaw specifically targets the member list functionality of the bulletin board system, where user input is not properly sanitized before being rendered back to the browser. This creates a persistent vector for attackers to execute malicious code against unsuspecting users who view the compromised member list page.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious input string containing script code that gets stored in the $letterbits variable within the memberlist.php script. When other users access the member list page, their browsers execute the injected script code in the context of their authenticated sessions. This enables attackers to steal session cookies, authentication tokens, and other sensitive information that users might have in their browser sessions. The vulnerability is particularly dangerous because it leverages the trust relationship between the web application and its users, allowing attackers to impersonate legitimate users and gain unauthorized access to their accounts. The attack vector is classified as a stored XSS vulnerability since the malicious script is permanently stored on the server and executed whenever users access the affected page.
The operational impact of CVE-2002-1678 extends beyond simple credential theft to encompass full account compromise and potential privilege escalation within the vBulletin environment. Attackers can leverage this vulnerability to access user accounts, modify user profiles, post malicious content, and potentially gain administrative privileges if they can compromise administrator accounts. The vulnerability also enables more sophisticated attacks such as session hijacking, where attackers can take over user sessions and maintain persistent access to the system. From an attacker's perspective, this vulnerability provides a reliable method for establishing a foothold within the web application, as it requires no special privileges or complex exploitation techniques beyond crafting malicious input. The attack can be executed through various means including social engineering, automated scanning tools, or direct injection attempts, making it particularly dangerous for public-facing bulletin board systems that rely on user-generated content.
Mitigation strategies for this vulnerability should focus on implementing comprehensive input validation and output encoding mechanisms. The primary defense involves sanitizing all user input parameters, particularly those used in dynamic content generation like $letterbits, by removing or encoding potentially dangerous characters such as angle brackets, quotes, and script tags. Organizations should implement proper HTML escaping routines that convert special characters into their HTML entity equivalents before rendering user-supplied content. Additionally, implementing Content Security Policy (CSP) headers can provide an additional layer of protection by restricting the sources from which scripts can be loaded and executed. The vulnerability also highlights the importance of regular security updates and patch management, as this issue was resolved in later versions of vBulletin. Security practitioners should also consider implementing web application firewalls and monitoring for suspicious input patterns that might indicate attempted XSS attacks. The remediation process should include thorough code review to identify similar vulnerabilities in other parts of the application and establish secure coding practices that prevent similar issues from occurring in future development cycles.