CVE-2019-6785 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 Denial of Service. Inputting an overly long string into a Markdown field could cause a denial of service.
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Analysis
by VulDB Data Team • 12/18/2023
The vulnerability identified as CVE-2019-6785 represents a denial of service flaw affecting GitLab Community and Enterprise Edition installations across multiple version ranges including versions prior to 11.5.8, 11.6.x before 11.6.6, and 11.7.x before 11.7.1. This issue stems from insufficient input validation within the Markdown processing functionality of the GitLab platform, creating a condition where malicious actors can exploit the system's handling of excessively long strings to disrupt normal operations. The vulnerability specifically targets the Markdown rendering engine which processes user-generated content within GitLab's interface, making it a critical concern for organizations relying on GitLab for version control and collaborative development environments.
The technical implementation of this vulnerability occurs when a user submits a Markdown field containing an overly long string that exceeds the system's acceptable input limits. During the rendering process, the Markdown parser attempts to process this excessive input which can cause the application to consume disproportionate computational resources or trigger memory allocation issues. This processing behavior leads to system performance degradation or complete service unavailability, effectively creating a denial of service condition. The flaw operates at the application layer and can be exploited without requiring authentication, making it particularly dangerous as any user with access to Markdown fields can potentially trigger the vulnerability. The underlying cause aligns with CWE-770, which addresses allocation of resources without proper limits or throttling mechanisms, and represents a classic example of resource exhaustion through malformed input handling.
The operational impact of CVE-2019-6785 extends beyond simple service disruption to potentially compromise the entire GitLab instance availability. Organizations utilizing GitLab for critical development workflows may experience complete service outages, preventing developers from accessing repositories, creating issues, or collaborating on code changes. The vulnerability affects core GitLab functionality including project management, issue tracking, and documentation features that rely on Markdown rendering. Attackers can exploit this weakness to target specific GitLab instances by submitting maliciously crafted Markdown content through various entry points such as issue descriptions, merge request comments, or wiki pages. The attack vector is particularly concerning because it can be executed through legitimate user actions, making it difficult to distinguish between normal usage and malicious activity. This vulnerability also aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a form of resource exhaustion that impacts system availability.
Mitigation strategies for CVE-2019-6785 primarily focus on implementing input validation and resource limiting measures within the Markdown processing pipeline. Organizations should immediately upgrade to GitLab versions 11.5.8, 11.6.6, or 11.7.1 respectively, which contain the necessary patches to address this vulnerability. System administrators should also consider implementing rate limiting and input length restrictions for Markdown fields to prevent exploitation even if the software upgrade is not immediately possible. Additional defensive measures include monitoring for unusual resource consumption patterns and implementing automated alerts when processing large Markdown inputs. The vulnerability demonstrates the importance of proper input sanitization and resource management in web applications, particularly those handling user-generated content. Security teams should also conduct regular vulnerability assessments to identify similar input validation weaknesses in other components of their GitLab infrastructure. Implementation of these mitigations should follow security best practices outlined in NIST SP 800-160 and ISO/IEC 27001 standards for secure software development practices.