CVE-2019-6784 in Community Edition
Summary
by MITRE
An issue was discovered in GitLab Community and Enterprise Edition before 11.5.8, 11.6.x before 11.6.6, and 11.7.x before 11.7.1. It allows XSS (issue 1 of 2). Markdown fields contain a lack of input validation and output encoding when processing KaTeX that results in a persistent XSS.
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Analysis
by VulDB Data Team • 12/18/2023
The vulnerability identified as CVE-2019-6784 represents a critical cross-site scripting flaw affecting GitLab Community and Enterprise Edition installations across multiple version streams. This security weakness resides within the markdown processing functionality of the platform, specifically when handling KaTeX mathematical notation rendering. The issue manifests as a persistent XSS vulnerability that can be exploited by attackers to inject malicious scripts into markdown fields, potentially compromising user sessions and data integrity. The vulnerability affects versions prior to 11.5.8, 11.6.6, and 11.7.1 respectively, indicating a widespread impact across the GitLab product line during this timeframe.
The technical root cause of this vulnerability stems from inadequate input validation and insufficient output encoding mechanisms within GitLab's markdown processing pipeline. When users create or edit content using markdown syntax that includes KaTeX mathematical expressions, the system fails to properly sanitize and encode the input data before rendering it to end users. This processing gap creates an opportunity for malicious actors to inject JavaScript code or other malicious payloads that persist in the system and execute whenever affected pages are viewed. The vulnerability is classified as persistent because the malicious content remains stored within the GitLab database and continues to execute against users who access the affected content. This flaw directly maps to CWE-79, which describes Cross-site Scripting vulnerabilities, and represents a failure in input validation and output encoding controls.
The operational impact of CVE-2019-6784 extends beyond simple script execution, as it provides attackers with potential access to sensitive user data and session information. When exploited, this vulnerability could enable attackers to steal user authentication tokens, access private repositories, modify project content, or even escalate privileges within the GitLab instance. The persistent nature of the vulnerability means that once a malicious payload is injected, it continues to affect users until the content is manually removed or the system is patched. This creates a particularly dangerous scenario for organizations using GitLab for code management and collaboration, as the attack surface includes all markdown-enabled fields throughout the platform including issue descriptions, wiki pages, and project documentation. The vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: JavaScript, as it enables JavaScript code execution within user contexts.
Organizations affected by this vulnerability should prioritize immediate patching of their GitLab installations to versions 11.5.8, 11.6.6, or 11.7.1 respectively, depending on their current version. Additionally, system administrators should implement temporary mitigations such as restricting user permissions for markdown editing capabilities, monitoring for suspicious content in markdown fields, and conducting thorough security audits of existing project documentation. The vulnerability demonstrates the critical importance of proper input validation and output encoding in web applications, particularly those handling user-generated content. Security teams should also consider implementing web application firewalls and content security policies to provide additional protection layers against similar attacks. This vulnerability serves as a reminder of the importance of comprehensive security testing for rich text processing features and the need for continuous security monitoring of collaboration platforms that handle sensitive code and documentation.