CVE-2015-2935 in MediaWiki
Summary
by MITRE
MediaWiki before 1.19.24, 1.2x before 1.23.9, and 1.24.x before 1.24.2 allows remote attackers to bypass the SVG filtering and obtain sensitive user information via a mixed case @import in a style element in an SVG file, as demonstrated by "@imporT."
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Analysis
by VulDB Data Team • 05/03/2022
This vulnerability resides in the MediaWiki content management system and represents a significant security flaw in the handling of Scalable Vector Graphics files. The issue stems from insufficient input validation and filtering mechanisms that fail to properly sanitize SVG content, particularly when processing style elements containing import directives. The vulnerability specifically targets versions prior to 1.19.24, 1.23.9, and 1.24.2, indicating a long-standing flaw that affected multiple release branches. The attack vector exploits the case-insensitive nature of the import directive by using mixed case characters such as "@imporT" to bypass security filters that only check for lowercase variations. This bypass technique allows attackers to inject malicious content that would otherwise be blocked by standard filtering mechanisms, potentially enabling the retrieval of sensitive user information through carefully crafted SVG files.
The technical implementation of this vulnerability involves the manipulation of SVG file parsing logic within MediaWiki's media handling subsystem. When MediaWiki processes SVG files, it attempts to filter out potentially dangerous elements while allowing legitimate vector graphics content. However, the filtering mechanism fails to account for case variations in the @import directive, creating a pathway for attackers to inject arbitrary content. This flaw operates at the application layer and can be classified under CWE-20, which represents improper input validation, and specifically aligns with CWE-15, which deals with external control of system or configuration settings. The vulnerability demonstrates a classic example of insecure input filtering where the system does not properly normalize or canonicalize input before processing, allowing attackers to circumvent security controls through simple case manipulation.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with a method to potentially access sensitive user data through the manipulation of SVG files. When an attacker successfully bypasses the SVG filtering, they can potentially inject malicious content that may lead to cross-site scripting attacks or data exfiltration. The vulnerability affects not just the display functionality but also the underlying security model of MediaWiki's media handling capabilities. Attackers could leverage this weakness to perform reconnaissance activities, gather user information, or potentially establish a foothold within systems that rely on MediaWiki for content management. The impact is particularly concerning given that SVG files are commonly used in web applications and can be easily embedded in various content types, making this vulnerability exploitable through multiple vectors.
Mitigation strategies for this vulnerability should focus on implementing proper input sanitization and normalization techniques within MediaWiki's SVG processing pipeline. Organizations should immediately upgrade to patched versions of MediaWiki that address this specific filtering issue, ensuring that all affected branches receive proper updates. The implementation of strict case normalization for all CSS directives within SVG files should be enforced, preventing attackers from using case variations to bypass security controls. Additionally, organizations should implement comprehensive monitoring for SVG file uploads and consider implementing additional content validation mechanisms beyond the default filtering. From a defensive perspective, this vulnerability aligns with ATT&CK technique T1059.007, which covers JavaScript and VBScript, as the exploitation may involve script injection through the SVG file processing. Network security controls should include inspection of SVG content for unusual patterns and implementation of web application firewalls that can detect and block such attempts to bypass filtering mechanisms.