CVE-2016-6334 in MediaWiki
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Parser::replaceInternalLinks2 method in MediaWiki before 1.23.15, 1.26.x before 1.26.4, and 1.27.x before 1.27.1 allows remote attackers to inject arbitrary web script or HTML via vectors involving replacement of percent encoding in unclosed internal links.
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Analysis
by VulDB Data Team • 12/21/2020
The CVE-2016-6334 vulnerability represents a critical cross-site scripting flaw discovered in MediaWiki's Parser::replaceInternalLinks2 method, affecting multiple versions of the popular wiki platform. This vulnerability stems from inadequate input validation and sanitization of user-provided content, specifically when processing internal links within wiki pages. The flaw manifests when MediaWiki encounters unclosed internal links that contain percent-encoded characters, creating an opportunity for malicious actors to inject arbitrary JavaScript code or HTML content into the application's output.
The technical exploitation of this vulnerability occurs through the manipulation of internal wiki links that utilize percent encoding, which is a standard method for encoding special characters in URLs and web addresses. When MediaWiki processes these malformed links, the Parser::replaceInternalLinks2 method fails to properly sanitize the input, allowing attackers to inject malicious scripts that execute in the context of other users' browsers. This particular weakness falls under CWE-79, which specifically addresses Cross-Site Scripting vulnerabilities, and demonstrates how improper handling of encoded characters can create persistent security gaps in web applications. The vulnerability is particularly dangerous because it operates within the core parsing functionality of MediaWiki, meaning that any user with permission to create or edit wiki pages could potentially exploit this flaw.
The operational impact of CVE-2016-6334 extends beyond simple script injection, as it can enable attackers to perform various malicious activities including session hijacking, data theft, and redirection to malicious websites. When exploited, the vulnerability allows remote attackers to execute arbitrary web scripts in the context of affected users' browsers, potentially leading to full compromise of user sessions and unauthorized access to sensitive information. The widespread adoption of MediaWiki across educational institutions, government organizations, and corporate environments means that this vulnerability could affect thousands of systems globally, making it a significant concern for security administrators and system operators. Attackers could leverage this vulnerability to steal user credentials, manipulate wiki content, or redirect users to phishing sites, all while appearing to originate from legitimate wiki pages.
Mitigation strategies for CVE-2016-6334 focus primarily on upgrading to patched versions of MediaWiki, specifically versions 1.23.15, 1.26.4, and 1.27.1, which contain the necessary code modifications to properly sanitize percent-encoded characters in internal links. Organizations should also implement additional defensive measures including input validation at multiple layers, content security policies to restrict script execution, and regular security audits of wiki content. The vulnerability's classification under the ATT&CK framework as a web application vulnerability highlights the need for comprehensive application security testing and monitoring. Security teams should also consider implementing web application firewalls and monitoring for suspicious link patterns that might indicate exploitation attempts, while ensuring that all users understand the risks of creating or editing content in shared wiki environments where such vulnerabilities could be leveraged against other users.