CVE-2011-4361 in MediaWiki
Summary
by MITRE
MediaWiki before 1.17.1 does not check for read permission before handling action=ajax requests, which allows remote attackers to obtain sensitive information by (1) leveraging the SpecialUpload::ajaxGetExistsWarning function, or by (2) leveraging an extension, as demonstrated by the CategoryTree, ExtTab, and InlineEditor extensions.
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Analysis
by VulDB Data Team • 11/28/2021
The vulnerability described in CVE-2011-4361 represents a critical access control flaw within MediaWiki versions prior to 1.17.1 that fundamentally undermines the system's permission model. This issue stems from the absence of proper read permission validation during ajax request processing, creating a pathway for unauthorized information disclosure that directly violates core security principles of least privilege and access control. The flaw exists specifically within the action=ajax request handling mechanism, where the application fails to verify whether the requesting user possesses adequate read permissions before executing sensitive operations.
The technical implementation of this vulnerability manifests through two primary attack vectors that exploit different aspects of MediaWiki's extension architecture. The first vector leverages the SpecialUpload::ajaxGetExistsWarning function, which is designed to check for file existence warnings during upload operations. However, this function does not properly validate user permissions, allowing attackers to probe the system for information about existing files or upload status without proper authorization. The second vector involves extension-specific implementations that lack proper access control checks, with the CategoryTree, ExtTab, and InlineEditor extensions serving as demonstrative examples of how third-party modules can inherit and propagate this vulnerability.
The operational impact of this vulnerability extends beyond simple information disclosure, as it enables attackers to systematically gather sensitive data about the MediaWiki installation and its contents. Through repeated exploitation of the ajax endpoints, adversaries can map out the structure of the wiki, identify potentially sensitive files, and gather intelligence about user permissions and system configuration. This reconnaissance capability significantly increases the risk of subsequent attacks, as it provides attackers with detailed knowledge of the target environment. The vulnerability affects not just the core MediaWiki functionality but also demonstrates how extension modules can introduce security gaps that compromise the entire platform.
This vulnerability aligns with CWE-284, which specifically addresses improper access control issues, and represents a clear violation of the principle that all operations should verify appropriate authorization before execution. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and reconnaissance, as attackers can gather information about the system without authentication. The lack of proper input validation and access control checks creates a persistent security weakness that can be exploited repeatedly, making it particularly dangerous for high-traffic wiki installations where the impact of information disclosure can be significant. Organizations using affected MediaWiki versions should prioritize immediate patching to address this access control bypass, as the vulnerability can be exploited remotely without requiring authentication credentials.