CVE-2023-39612
📋 TL;DR
This cross-site scripting (XSS) vulnerability in FileBrowser allows authenticated attackers to escalate privileges to Administrator by tricking users into interacting with malicious HTML files or URLs. The vulnerability affects FileBrowser installations before version 2.23.0 where users have authenticated access.
💻 Affected Systems
- FileBrowser
📦 What is this software?
Filebrowser by Filebrowser
⚠️ Risk & Real-World Impact
Worst Case
Complete administrative takeover of the FileBrowser instance, allowing attackers to read, modify, or delete all files, change configurations, and potentially pivot to underlying systems.
Likely Case
Privilege escalation from regular user to administrator, enabling unauthorized access to sensitive files and system configuration.
If Mitigated
Limited impact if proper input validation and output encoding are implemented, or if users don't interact with malicious content.
🎯 Exploit Status
Exploitation requires authenticated user interaction with crafted content, making social engineering a component of successful attacks.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.23.0 and later
Vendor Advisory: https://github.com/filebrowser/filebrowser/commit/b508ac3d4f7f0f75d6b49c99bdc661a6d2173f30
Restart Required: Yes
Instructions:
1. Backup your FileBrowser configuration and data. 2. Stop the FileBrowser service. 3. Update to version 2.23.0 or later using your package manager or by downloading from GitHub. 4. Restart the FileBrowser service. 5. Verify the update was successful.
🔧 Temporary Workarounds
Disable HTML file uploads
allPrevent users from uploading HTML files that could contain malicious scripts
Configure FileBrowser settings to block .html file uploads
Restrict user permissions
allLimit authenticated users to read-only access where possible
Set user permissions to 'read' only in FileBrowser configuration
🧯 If You Can't Patch
- Implement strict Content Security Policy (CSP) headers to prevent script execution
- Isolate FileBrowser instance behind authentication proxy with additional security controls
🔍 How to Verify
Check if Vulnerable:
Check FileBrowser version: if version is below 2.23.0, the system is vulnerableCheck Version:
filebrowser versionVerify Fix Applied:
Verify FileBrowser version is 2.23.0 or higher and test that HTML file uploads are properly sanitized📡 Detection & Monitoring
Log Indicators:
- Unusual privilege escalation events
- Multiple failed authentication attempts followed by successful admin access
- Suspicious file uploads with HTML extensions
Network Indicators:
- Unexpected outbound connections from FileBrowser server
- Traffic patterns suggesting data exfiltration
SIEM Query:
source="filebrowser" AND (event="privilege_escalation" OR event="admin_login" from non-admin user)🔗 References
- https://febin0x4e4a.wordpress.com/2023/09/15/xss-in-filebrowser-leads-to-admin-account-takeover-in-filebrowser/
- https://github.com/filebrowser/filebrowser/commit/b508ac3d4f7f0f75d6b49c99bdc661a6d2173f30
- https://github.com/filebrowser/filebrowser/issues/2570
- https://febin0x4e4a.wordpress.com/2023/09/15/xss-in-filebrowser-leads-to-admin-account-takeover-in-filebrowser/
- https://github.com/filebrowser/filebrowser/commit/b508ac3d4f7f0f75d6b49c99bdc661a6d2173f30
- https://github.com/filebrowser/filebrowser/issues/2570
