CVE-2026-19619 in GitLab
Summary
by MITRE • 09/16/2026
GitLab has remediated an issue in GitLab CE/EE affecting all versions from 19.0 before 19.1.8, 19.2 before 19.2.6, and 19.3 before 19.3.2 that under certain conditions could have allowed an unauthenticated user to execute arbitrary JavaScript in the context of a targeted user's session due to improper sanitization of pasted HTML content in the Content Editor.
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Analysis
by VulDB Data Team • 09/16/2026
The vulnerability identified within GitLab Community Edition and Enterprise Edition versions prior to 19.1.8, 19.2.6, and 19.3.2 represents a critical security flaw rooted in inadequate input validation mechanisms. Specifically, the Content Editor component failed to properly sanitize HTML content when users pasted rich text into the interface. This deficiency allowed malicious actors to inject arbitrary JavaScript code that would be executed within the context of an authenticated user's session. The issue is particularly severe because it affects a wide range of older versions and can potentially impact unauthenticated attackers who might trick targeted users into interacting with crafted content, thereby bypassing standard authentication controls through social engineering or cross-site scripting vectors.
From a technical perspective, this flaw aligns closely with CWE-79, which classifies Improper Neutralization of Input During Web Page Generation commonly known as Cross-Site Scripting (XSS). The root cause lies in the application's failure to strip or escape dangerous script tags and event handlers embedded within pasted HTML. When a user copies content from an external source containing malicious scripts and pastes it into the GitLab Content Editor, the backend processing does not adequately filter these elements before rendering them back to the browser. Consequently, when another user views this content, their browser executes the injected JavaScript as if it were part of the legitimate application code. This execution occurs within the same origin policy context, granting the attacker access to sensitive data and session tokens associated with the victim's account.
The operational impact of this vulnerability is significant for organizations relying on GitLab for version control and collaborative development. An unauthenticated or low-privilege user could exploit this flaw to perform actions such as stealing session cookies, hijacking administrative sessions, defacing web pages, or redirecting users to phishing sites. In enterprise environments where sensitive intellectual property and code repositories are hosted, the compromise of even a single account can lead to broader system infiltration if that account possesses elevated privileges. Furthermore, because the attack vector involves pasted content, it is highly susceptible to social engineering tactics, making detection difficult without robust monitoring and user awareness programs.
This incident also maps to several techniques within the MITRE ATT&CK framework, notably T1059 Command and Scripting Interpreter for JavaScript execution and potentially T1204 User Execution if the attack relies on convincing a victim to open or interact with malicious content. The ability to execute arbitrary code in the context of another user's session underscores the importance of strict output encoding and input validation practices in web application development. Security teams must recognize that modern rich text editors often introduce complex parsing layers where sanitization logic can be bypassed through obfuscation techniques, necessitating defense-in-depth strategies rather than reliance on single-point controls.
To mitigate this risk, organizations running affected versions of GitLab CE or EE should immediately upgrade to the patched releases: 19.1.8, 19.2.6, or 19.3.2 and later. These updates include enhanced sanitization routines that properly neutralize dangerous HTML elements before they are rendered in the browser environment. Additionally, implementing Content Security Policy (CSP) headers can provide an additional layer of protection by restricting the sources from which scripts can be loaded and executed, thereby limiting the impact even if a bypass occurs. Regular security audits and penetration testing focused on input validation weaknesses should also be conducted to identify similar vulnerabilities in other components of the GitLab instance or integrated third-party applications.