CVE-2024-6886: Gitea Open Source Git Server XSS Flaw

CVE-2024-6886 Overview

CVE-2024-6886 is a Stored Cross-Site Scripting (XSS) vulnerability affecting Gitea Open Source Git Server version 1.22.0. This vulnerability stems from improper neutralization of input during web page generation, allowing attackers to inject malicious scripts that persist in the application and execute in the browsers of other users who view the affected content.

Stored XSS vulnerabilities are particularly dangerous in collaborative development platforms like Gitea, as malicious payloads can be embedded in repository content, issues, comments, or other user-generated areas, potentially compromising developer accounts and sensitive source code.

Critical Impact

This vulnerability enables attackers to execute arbitrary JavaScript in victim browsers, potentially leading to session hijacking, credential theft, repository manipulation, and lateral movement across development infrastructure.

Affected Products

• Gitea Open Source Git Server version 1.22.0

Discovery Timeline

• 2024-08-06 - CVE-2024-6886 published to NVD
• 2024-08-06 - Last updated in NVD database

Technical Details for CVE-2024-6886

Vulnerability Analysis

This vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation). Gitea version 1.22.0 fails to properly sanitize user-supplied input before rendering it in web pages, enabling persistent storage and execution of malicious JavaScript code.

In a Git collaboration platform, numerous input vectors exist where users can submit content that is later displayed to other users—including repository descriptions, issue titles, comments, pull request discussions, wiki pages, and file content previews. When input sanitization fails in any of these areas, attackers can inject scripts that execute whenever another user views the tainted content.

The exploitation potential is significant given that Gitea instances often host proprietary source code and are accessed by developers with elevated privileges. Successful exploitation could allow attackers to steal authentication tokens, modify repository contents, create backdoored releases, or pivot to connected CI/CD systems.

Root Cause

The root cause of CVE-2024-6886 is insufficient input validation and output encoding in the web page generation process. The application fails to properly escape or sanitize user-controlled content before incorporating it into HTML responses, allowing script tags and JavaScript event handlers to be interpreted by the browser rather than rendered as text.

Attack Vector

The attack vector is network-based and requires no special privileges or user interaction beyond the victim viewing the malicious content. An attacker can exploit this vulnerability by:

1. Submitting specially crafted input containing JavaScript payloads to a persistent storage location within Gitea
2. The malicious content is stored in the database or file system
3. When other users browse to pages displaying this content, the injected scripts execute in their browser context
4. The attacker can then exfiltrate session cookies, perform actions on behalf of the victim, or redirect users to phishing pages

The vulnerability mechanism exploits insufficient output encoding in the rendering pipeline. When user-supplied content is incorporated into HTML responses without proper escaping, browser parsing interprets embedded script elements as executable code rather than display text. For detailed technical information, see the GitHub Pull Request #31200 which addresses this issue.

Detection Methods for CVE-2024-6886

Indicators of Compromise

• Unusual JavaScript patterns in repository content, issue descriptions, comments, or wiki pages
• Unexpected network requests from user browsers to external domains when viewing Gitea pages
• Authentication tokens or session cookies appearing in external server logs
• User reports of unexpected behavior or redirects when using the Gitea interface

Detection Strategies

• Implement Content Security Policy (CSP) headers with strict script-src directives to detect and block unauthorized script execution
• Deploy Web Application Firewall (WAF) rules to identify XSS payloads in incoming requests
• Monitor Gitea access logs for patterns indicating automated injection attempts
• Configure browser security headers and enable XSS auditor logging where available

Monitoring Recommendations

• Enable detailed access logging for the Gitea web interface and review for suspicious input patterns
• Implement network monitoring for unusual outbound connections from client browsers accessing Gitea
• Set up alerts for modifications to sensitive repository settings or user permissions that may indicate account compromise
• Monitor for creation of new administrative accounts or privilege escalation events

How to Mitigate CVE-2024-6886

Immediate Actions Required

• Upgrade Gitea to version 1.22.1 or later immediately to apply the security fix
• Review repository content, issues, and comments for potentially malicious JavaScript code
• Rotate session tokens and credentials for users who may have accessed compromised content
• Implement Content Security Policy headers to provide defense-in-depth against XSS attacks

Patch Information

Gitea has released version 1.22.1 which addresses this stored XSS vulnerability. The fix is documented in the Gitea Release Announcement and the technical changes can be reviewed in GitHub Pull Request #31200.

Organizations running Gitea 1.22.0 should upgrade to 1.22.1 or the latest available version as soon as possible.

Workarounds

• Deploy a Web Application Firewall (WAF) with XSS filtering capabilities in front of the Gitea instance
• Implement strict Content Security Policy headers to prevent inline script execution
• Restrict user registration and access to trusted users until the patch can be applied
• Consider temporarily disabling features that allow rich content input such as issue comments or wiki pages

# Example: Add Content Security Policy headers in reverse proxy (nginx)
# Add to nginx server block configuration
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; font-src 'self';" always;
add_header X-Content-Type-Options "nosniff" always;
add_header X-XSS-Protection "1; mode=block" always;