CVE-2026-25889
📋 TL;DR
A case-sensitivity flaw in File Browser's password validation allows authenticated users to change passwords without providing the current password. By using 'Password' instead of 'password' in API requests, attackers can bypass verification and take over accounts. This affects all File Browser instances prior to version 2.57.1.
💻 Affected Systems
- File Browser
📦 What is this software?
Filebrowser by Filebrowser
⚠️ Risk & Real-World Impact
Worst Case
Complete account takeover leading to unauthorized file access, data theft, or system compromise if admin accounts are affected.
Likely Case
Privilege escalation where authenticated users change passwords to gain persistent access or lock out legitimate users.
If Mitigated
Limited impact if strong authentication controls, network segmentation, and monitoring are in place.
🎯 Exploit Status
Exploitation requires a valid JWT token obtained through XSS, session hijacking, or credential theft. The bypass technique is simple and well-documented.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.57.1
Vendor Advisory: https://github.com/filebrowser/filebrowser/security/advisories/GHSA-hxw8-4h9j-hq2r
Restart Required: Yes
Instructions:
1. Backup current configuration and data. 2. Stop File Browser service. 3. Update to version 2.57.1 or later. 4. Restart File Browser service. 5. Verify functionality.
🔧 Temporary Workarounds
Disable password change functionality
allTemporarily disable password change API endpoints until patching is complete.
Modify configuration to remove or restrict access to /api/users/*/password endpoints
Implement API request validation
allAdd middleware to normalize field names and reject requests with unexpected case variations.
Implement request preprocessing to convert all field names to lowercase before validation
🧯 If You Can't Patch
- Implement network segmentation to restrict access to File Browser instances
- Enable detailed logging and monitoring for password change attempts and review regularly
🔍 How to Verify
Check if Vulnerable:
Check if File Browser version is below 2.57.1. Attempt password change with 'Password' field name instead of 'password' (requires valid JWT).Check Version:
filebrowser versionVerify Fix Applied:
After updating to 2.57.1+, attempt password change with 'Password' field name - it should fail with proper validation error.📡 Detection & Monitoring
Log Indicators:
- Unusual password change requests
- API calls with 'Password' field name instead of 'password'
- Multiple failed authentication attempts followed by password changes
Network Indicators:
- POST requests to /api/users/*/password endpoints with unusual field names
- Traffic patterns showing password changes without preceding successful login
SIEM Query:
source="filebrowser" AND (uri_path="/api/users/*/password" OR message="*password*change*")