CVE-2018-19570 in Community Edition
Summary
by MITRE
GitLab CE/EE, versions 11.3 before 11.3.11, 11.4 before 11.4.8, and 11.5 before 11.5.1, are vulnerable to an XSS vulnerability in Markdown fields via unrecognized HTML tags.
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Analysis
by VulDB Data Team • 06/23/2024
This vulnerability exists in GitLab Community Edition and Enterprise Edition versions prior to specific patch releases, representing a cross-site scripting flaw that specifically affects Markdown rendering functionality. The issue stems from insufficient input validation and sanitization of HTML content within Markdown fields, allowing malicious actors to inject harmful scripts that execute in the context of other users' browsers. The vulnerability is particularly concerning because Markdown fields are commonly used throughout GitLab for issue descriptions, commit messages, and wiki content, making it a widespread attack vector across multiple application components. This flaw enables attackers to bypass standard security controls that typically protect against XSS attacks by leveraging the legitimate Markdown processing functionality that should safely handle user input.
The technical implementation of this vulnerability involves GitLab's Markdown parser failing to properly sanitize HTML tags that are not recognized or explicitly allowed within the Markdown specification. When users create content containing unrecognized HTML elements within Markdown fields, the system does not adequately filter or escape these elements before rendering them in web pages. This creates an environment where attackers can embed malicious script tags, event handlers, or other HTML constructs that execute when other users view the affected content. The vulnerability specifically impacts versions where the HTML sanitization logic was insufficient to prevent the execution of potentially dangerous markup, allowing for the injection of JavaScript code that can steal session cookies, redirect users to malicious sites, or perform other harmful actions.
The operational impact of this vulnerability is significant as it allows for persistent cross-site scripting attacks that can affect any user who views affected Markdown content. Attackers can craft malicious Markdown that, when rendered, executes code in the browser context of other users, potentially leading to session hijacking, data exfiltration, or privilege escalation within the GitLab environment. The vulnerability affects a broad range of GitLab functionality including issue tracking, wiki pages, and commit messages, making it particularly dangerous as it can be exploited across multiple attack surfaces. Users with administrative privileges could potentially leverage this vulnerability to gain elevated access or compromise the entire GitLab instance, especially if the application lacks proper input validation at multiple layers of the application stack.
Mitigation strategies for this vulnerability include applying the official security patches released by GitLab for versions 11.3.11, 11.4.8, and 11.5.1, which contain updated HTML sanitization logic that properly handles unrecognized HTML tags in Markdown fields. Organizations should also implement additional security measures such as content security policies that restrict script execution, regular security scanning of user-generated content, and comprehensive input validation at multiple application layers. The vulnerability aligns with CWE-79 Improper Neutralization of Input During Web Page Generation, which specifically addresses the improper handling of user input that leads to XSS vulnerabilities. From an ATT&CK framework perspective, this vulnerability maps to T1059.001 Command and Scripting Interpreter: PowerShell and T1566 Phishing, as attackers can use this vector to deliver malicious payloads to unsuspecting users and establish persistent access to the GitLab environment. Organizations should also consider implementing automated monitoring for suspicious Markdown content and regular security awareness training for developers who create content within GitLab environments.