CVE-2025-1763: GitLab EE XSS Vulnerability

CVE-2025-1763 Overview

A cross-site scripting (XSS) vulnerability has been discovered in GitLab Enterprise Edition (EE) that enables attackers to execute malicious scripts in a user's browser while bypassing Content Security Policy (CSP) protections. This vulnerability affects GitLab EE across multiple version branches, potentially exposing organizations using affected versions to script injection attacks that can compromise user sessions, steal sensitive data, and perform unauthorized actions within the GitLab platform.

Critical Impact

Successful exploitation allows attackers to bypass CSP protections and execute arbitrary JavaScript in victim browsers, potentially leading to session hijacking, credential theft, and unauthorized access to GitLab repositories and CI/CD pipelines.

Affected Products

• GitLab Enterprise Edition versions 16.6 before 17.9.7
• GitLab Enterprise Edition versions 17.10 before 17.10.5
• GitLab Enterprise Edition version 17.11.0 (fixed in 17.11.1)

Discovery Timeline

• 2025-05-30 - CVE-2025-1763 published to NVD
• 2025-08-08 - Last updated in NVD database

Technical Details for CVE-2025-1763

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The flaw allows attackers to inject malicious scripts that execute in the context of a victim's authenticated session within GitLab EE.

What makes this vulnerability particularly concerning is the ability to bypass Content Security Policy (CSP) protections. CSP is a critical browser security mechanism designed to prevent XSS attacks by restricting the sources from which scripts can be loaded and executed. The ability to circumvent these protections significantly increases the attack's effectiveness and reduces the defenses available to organizations.

The attack requires network access and user interaction, meaning an attacker must craft a malicious payload and convince an authenticated GitLab user to trigger it. Upon successful exploitation, the attacker can execute JavaScript with the full privileges of the victim user, potentially accessing private repositories, CI/CD secrets, API tokens, and other sensitive data stored within GitLab.

Root Cause

The vulnerability stems from improper input sanitization in GitLab EE's web interface under specific conditions. User-supplied input is not adequately validated or encoded before being rendered in the browser, allowing specially crafted payloads to escape the intended context and execute as JavaScript code. Additionally, the CSP implementation contains a flaw that permits script execution that should otherwise be blocked by policy rules.

Attack Vector

The attack is network-based and requires the attacker to have low-privilege access to the GitLab instance. The exploitation flow involves:

1. An attacker with basic GitLab access crafts a malicious XSS payload designed to bypass CSP restrictions
2. The payload is injected through a vulnerable input field or parameter within GitLab EE
3. When an authenticated victim user views the page containing the payload, the malicious script executes
4. The script runs with the victim's session privileges, enabling data exfiltration, session hijacking, or unauthorized actions

The vulnerability requires user interaction (the victim must navigate to or view the malicious content), but once triggered, the impact extends beyond the victim's browser session due to the scope change characteristic, potentially affecting other users and systems.

Detection Methods for CVE-2025-1763

Indicators of Compromise

• Unusual JavaScript execution patterns in GitLab web interface logs
• Unexpected HTTP requests to external domains from GitLab user sessions
• Reports of users experiencing unexpected behavior or redirects within GitLab
• Evidence of session token exfiltration or unauthorized API calls using stolen credentials

Detection Strategies

• Monitor web application firewall (WAF) logs for XSS attack signatures targeting GitLab endpoints
• Implement browser-side anomaly detection for CSP violation reports that may indicate exploitation attempts
• Review GitLab access logs for suspicious patterns indicating compromised user sessions
• Deploy endpoint detection solutions to identify malicious script execution in user browsers

Monitoring Recommendations

• Enable and review CSP violation reporting to detect bypass attempts
• Configure SIEM rules to alert on unusual GitLab API activity patterns following user web sessions
• Monitor for unexpected outbound connections from systems accessing GitLab
• Regularly audit GitLab user activity logs for signs of account compromise

How to Mitigate CVE-2025-1763

Immediate Actions Required

• Upgrade GitLab EE to version 17.9.7, 17.10.5, or 17.11.1 or later immediately
• Audit recent user activity for signs of compromise if running an affected version
• Review and rotate sensitive credentials including API tokens and CI/CD secrets
• Notify users to verify recent account activity and report suspicious behavior

Patch Information

GitLab has released security patches addressing this vulnerability. Organizations should upgrade to the following fixed versions based on their current deployment:

For detailed upgrade instructions and release notes, refer to the GitLab Issue Report and the HackerOne Vulnerability Report.

Workarounds

• If immediate patching is not possible, implement additional WAF rules to filter potential XSS payloads targeting GitLab
• Consider restricting access to GitLab to trusted networks while upgrade planning is underway
• Enable strict CSP headers at the reverse proxy or load balancer level as an additional defense layer
• Educate users about the risks of clicking suspicious links or accessing untrusted content within GitLab