CVE-2021-40668
📋 TL;DR
This path traversal vulnerability in Android HTTP File Server 1.4.1 allows attackers to access, list, and modify files outside the intended directory. It affects users running this specific version of the file server application on Android devices. The vulnerability enables unauthorized file operations through specially crafted requests.
💻 Affected Systems
- HTTP File Server by slowscript
📦 What is this software?
Http File Server by Http File Server Project
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of device file system including sensitive data theft, malware installation, or device takeover if combined with other vulnerabilities.
Likely Case
Unauthorized access to sensitive files stored on the device, potential data exfiltration, and file system manipulation.
If Mitigated
Limited impact with proper network segmentation and access controls, restricting exposure to trusted networks only.
🎯 Exploit Status
Simple path traversal payloads can be used; no authentication required for exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: None available
Restart Required: No
Instructions:
Uninstall the vulnerable application and replace with alternative file server solutions.
🔧 Temporary Workarounds
Network Isolation
allRestrict application access to trusted networks only
Configure firewall to block external access to port used by HTTP File Server
Application Removal
androidUninstall vulnerable application completely
adb uninstall slowscript.httpfileserver
Settings > Apps > HTTP File Server > Uninstall
🧯 If You Can't Patch
- Disable or uninstall the HTTP File Server application immediately
- Implement strict network segmentation and firewall rules to prevent external access
🔍 How to Verify
Check if Vulnerable:
Check app version in Android settings: Settings > Apps > HTTP File Server > App infoCheck Version:
adb shell dumpsys package slowscript.httpfileserver | grep versionNameVerify Fix Applied:
Confirm application is no longer installed or verify network access is properly restricted📡 Detection & Monitoring
Log Indicators:
- Unusual file access patterns
- Requests containing '../' sequences
- Access to files outside expected directories
Network Indicators:
- HTTP requests with path traversal payloads to file server port
- Unusual file download patterns
SIEM Query:
http.url:*../* AND dest_port:[PORT] AND app:"HTTP File Server"