CVE-2025-53826
📋 TL;DR
File Browser version 2.39.0 has an authentication flaw where JWT tokens remain valid indefinitely even after user logout. This allows attackers with stolen tokens to maintain unauthorized access to file management functions. All deployments using the vulnerable version are affected.
💻 Affected Systems
- File Browser
📦 What is this software?
Filebrowser by Filebrowser
⚠️ Risk & Real-World Impact
Worst Case
Attackers gain persistent administrative access to file systems, enabling data theft, ransomware deployment, or complete system compromise through file manipulation.
Likely Case
Unauthorized users maintain access to sensitive files after legitimate sessions end, leading to data breaches or unauthorized modifications.
If Mitigated
With proper network segmentation and monitoring, impact is limited to the specific File Browser instance without lateral movement.
🎯 Exploit Status
Exploitation requires obtaining a valid JWT token through other means, but token reuse is trivial once obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: None available
Vendor Advisory: https://github.com/filebrowser/filebrowser/security/advisories/GHSA-7xwp-2cpp-p8r7
Restart Required: Yes
Instructions:
No official patch exists. Monitor GitHub repository for updates and apply immediately when available.
🔧 Temporary Workarounds
Implement JWT Token Revocation
allAdd server-side token blacklisting or implement short token expiration with refresh mechanisms
# Requires custom implementation - no ready commands
Force Token Expiration
allModify authentication logic to check token validity against logout timestamps
# Requires code modification - no ready commands
🧯 If You Can't Patch
- Isolate File Browser instance behind VPN or strict network ACLs
- Implement session monitoring and alert on suspicious long-lived sessions
🔍 How to Verify
Check if Vulnerable:
Check File Browser version via web interface or configuration filesCheck Version:
Check web interface or config file for version 2.39.0Verify Fix Applied:
Test logout functionality - tokens should become invalid after logout📡 Detection & Monitoring
Log Indicators:
- Multiple successful authentications from same token over extended periods
- Token usage after logout events
Network Indicators:
- Sustained API calls with same authorization header over days/weeks
SIEM Query:
auth_token="*" AND event="api_call" | stats count by auth_token | where count > threshold AND time_range > 24h