CVE-2012-4377 in MediaWiki
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in MediaWiki before 1.18.5 and 1.19.x before 1.19.2 allows remote attackers to inject arbitrary web script or HTML via a File: link to a nonexistent image.
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Analysis
by VulDB Data Team • 04/12/2021
The CVE-2012-4377 vulnerability represents a critical cross-site scripting flaw in MediaWiki software that affected versions prior to 1.18.5 and 1.19.x before 1.19.2. This vulnerability resides in the MediaWiki platform's handling of file links, specifically when users attempt to reference non-existent images through File: links. The flaw allows remote attackers to inject malicious web scripts or HTML code into the application's output, creating a persistent security risk for all users interacting with vulnerable MediaWiki installations.
The technical mechanism behind this vulnerability stems from inadequate input validation and output sanitization within MediaWiki's file link processing system. When a user creates a File: link to an image that does not exist within the wiki's media repository, the application fails to properly escape or filter the user-supplied URL parameters before rendering them in the browser context. This improper handling creates an XSS attack vector where malicious actors can craft specially formatted File: links containing script tags or other malicious HTML content that executes in the context of other users' browsers. The vulnerability is particularly dangerous because it leverages the legitimate MediaWiki functionality for referencing files, making the malicious code appear to originate from a trusted source within the wiki environment.
The operational impact of CVE-2012-4377 extends beyond simple script execution, as it can enable sophisticated attack chains that compromise user sessions and facilitate further exploitation. Attackers can leverage this vulnerability to steal session cookies, redirect users to malicious sites, or inject persistent malware into the wiki environment. The vulnerability affects not only individual users but also the integrity of entire wiki communities, as compromised installations can serve as attack platforms for targeting multiple users simultaneously. This risk is particularly severe in collaborative environments where MediaWiki serves as a central knowledge repository, potentially allowing attackers to manipulate content, deface pages, or establish backdoors for continued access. The vulnerability also aligns with CWE-79, which classifies cross-site scripting as a critical weakness in web applications, and maps to ATT&CK technique T1566, specifically the use of malicious file content to establish initial access.
Organizations and administrators should immediately implement comprehensive mitigation strategies to address this vulnerability. The primary remediation involves upgrading to MediaWiki versions 1.18.5 or 1.19.2 and later, which contain proper input validation and output escaping mechanisms for file links. Additionally, administrators should implement strict input filtering for all user-generated content, particularly in areas where File: links are permitted. Network-level protections such as web application firewalls can provide additional defense-in-depth, though they should not replace proper software updates. Regular security audits of wiki content and user permissions should be conducted to detect potential exploitation attempts. The vulnerability also highlights the importance of maintaining current security practices, including regular software updates, proper access controls, and user education about the risks of clicking untrusted links within wiki environments. Organizations using older MediaWiki versions should consider implementing temporary workarounds such as disabling File: link functionality or restricting user permissions until proper upgrades can be completed, as the vulnerability can be exploited through various attack vectors including user-generated content, external link insertion, and automated scanning tools that target known vulnerable patterns.