CVE-2018-6200 in vBulletin
Summary
by MITRE
vBulletin 3.x.x and 4.2.x through 4.2.5 has an open redirect via the redirector.php url parameter.
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Analysis
by VulDB Data Team • 12/27/2019
The vulnerability identified as CVE-2018-6200 affects vBulletin versions 3.x.x and 4.2.x through 4.2.5, specifically targeting the redirector.php script which processes the url parameter. This represents a classic open redirect vulnerability that allows attackers to manipulate the redirect functionality to forward users to malicious external domains. The flaw exists within the application's authentication and session management mechanisms where user-provided URLs are not properly validated or sanitized before being used for redirection operations. The vulnerability stems from inadequate input validation and sanitization processes that fail to properly examine the url parameter for potentially dangerous redirects.
The technical implementation of this vulnerability exploits the lack of proper validation in the redirector.php script which accepts user input through the url parameter and directly uses it to construct redirect headers without sufficient sanitization. This allows an attacker to craft malicious URLs that appear legitimate but redirect users to phishing sites or malicious domains. The flaw operates at the application layer and can be exploited through simple parameter manipulation techniques. According to CWE standards, this maps to CWE-601 Open Redirect vulnerability where the application redirects users to external domains without proper validation. The vulnerability is particularly concerning because it can be leveraged for phishing attacks, social engineering campaigns, and credential theft operations.
From an operational impact perspective, this vulnerability enables attackers to conduct sophisticated phishing campaigns by making malicious redirects appear to originate from legitimate vBulletin domains. Users may be tricked into visiting malicious sites that appear to be legitimate vBulletin pages, potentially leading to credential compromise or malware installation. The vulnerability affects organizations using outdated vBulletin versions, creating a significant risk for enterprises that have not updated their software. The attack surface is broad since the redirect functionality is typically used for legitimate purposes such as login redirects, forum navigation, and user authentication flows. Security analysts should consider this vulnerability in the context of ATT&CK framework where it maps to T1566 Phishing and T1071.004 Application Layer Protocol: Web Protocols, as it enables attackers to manipulate web application behavior for malicious purposes.
Organizations should immediately implement mitigations including patching to the latest available versions of vBulletin, implementing proper input validation for all redirect parameters, and adding security headers to prevent unintended redirects. Additional protective measures include monitoring for suspicious redirect patterns, implementing web application firewalls, and conducting regular security assessments. The vulnerability underscores the importance of maintaining up-to-date software versions and proper input sanitization practices. Security teams should also consider implementing redirect validation mechanisms that verify destination URLs against approved domain lists and employ proper logging of redirect operations for forensic analysis. Organizations with legacy vBulletin installations should prioritize migration to supported versions to eliminate exposure to this and similar vulnerabilities.