Overview
This report discusses the details of a discovered vulnerability, CVE-2025-4439, found in GitLab CE/EE versions ranging from 15.10 to 18.2.1. This vulnerability presents a significant risk as it allows an authenticated user to perform cross-site scripting (XSS) attacks when the instance is served through certain content delivery networks (CDNs). Given the widespread use of GitLab for version control and project management, it is crucial for organizations to understand and mitigate this risk.
Vulnerability Summary
CVE ID: CVE-2025-4439
Severity: High (7.7 CVSS Score)
Attack Vector: Network
Privileges Required: Low
User Interaction: Required
Impact: Potential system compromise or data leakage
Affected Products
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Product | Affected Versions
GitLab CE/EE | 15.10 – 18.0.4
GitLab CE/EE | 18.1 – 18.1.2
GitLab CE/EE | 18.2 – 18.2.0
How the Exploit Works
CVE-2025-4439 exploits a flaw in the handling of certain CDNs by the GitLab instance. An authenticated user can inject malicious scripts into the web application, which are then executed in the user’s browser when they access the web app through the affected CDNs. This is a classic Cross-Site Scripting attack, a common web security vulnerability.
Conceptual Example Code
POST /vulnerable/cdn HTTP/1.1
Host: target.example.com
Content-Type: application/json
{
"script": "<script>malicious_code_here</script>"
}This is a conceptual example demonstrating how the payload with malicious script might be sent to the vulnerable endpoint.
Mitigation Guidance
To mitigate this vulnerability, users are advised to immediately apply the vendor patch when available. As a temporary mitigation, users can employ Web Application Firewalls (WAFs) or Intrusion Detection Systems (IDS) to detect and prevent exploitation of this vulnerability.
