CVE-2017-8814 in MediaWiki
Summary
by MITRE
The language converter in MediaWiki before 1.27.4, 1.28.x before 1.28.3, and 1.29.x before 1.29.2 allows attackers to replace text inside tags via a rule definition followed by "a lot of junk."
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Analysis
by VulDB Data Team • 01/23/2021
The vulnerability identified as CVE-2017-8814 represents a critical security flaw in MediaWiki's language converter component that affects multiple version streams including 1.27.4, 1.28.3, and 1.29.2. This issue stems from inadequate input validation and sanitization within the parser that processes language conversion rules, creating an avenue for malicious actors to manipulate content through carefully crafted rule definitions. The vulnerability specifically targets the parser's handling of text replacement operations within HTML tags, allowing attackers to inject arbitrary content that bypasses normal security controls.
The technical exploitation mechanism leverages a specific pattern where an attacker defines a language conversion rule followed by an excessive amount of irrelevant data or "junk" characters. This technique exploits a buffer handling or parsing limitation within the language converter module, where the system fails to properly validate the boundaries of text replacement operations. The flaw enables attackers to manipulate the parser's behavior by injecting content that gets processed and rendered within HTML tags, effectively bypassing standard content sanitization measures. This vulnerability operates at the intersection of CWE-129 Input Validation and CWE-776 Improper Restriction of Recursive Entity References, creating a scenario where malformed input can cause unintended text substitution within tags.
The operational impact of this vulnerability extends beyond simple content manipulation to potentially enable more sophisticated attacks including cross-site scripting, data injection, and content spoofing. An attacker could exploit this weakness to inject malicious scripts, modify critical content, or manipulate user interfaces within MediaWiki environments. The vulnerability particularly affects collaborative platforms and wikis where users can contribute content, as it allows for subtle but impactful modifications that may go unnoticed during routine content review processes. The attack vector is especially concerning in environments where MediaWiki serves as a primary content management system for organizations relying on its security properties.
Mitigation strategies for CVE-2017-8814 should prioritize immediate patching of affected MediaWiki installations to versions 1.27.4, 1.28.3, or 1.29.2, which contain the necessary fixes for the language converter parsing issue. Organizations should also implement additional input validation measures at the application level, including stricter sanitization of rule definitions and content processing pipelines. The remediation process should include comprehensive testing to ensure that language conversion features function correctly without introducing new vulnerabilities. Security teams should monitor for any signs of exploitation attempts and consider implementing web application firewalls with rules specifically designed to detect and block suspicious language conversion rule patterns. This vulnerability highlights the importance of proper input validation and the potential for seemingly benign parsing features to become attack vectors when not properly secured against malicious input manipulation.