CVE-2021-21894
📋 TL;DR
This CVE describes an authenticated directory traversal vulnerability in Lantronix PremierWave 2050's Web Manager FsTFtp functionality. An attacker with valid credentials can exploit this to read or overwrite arbitrary files on the system. This affects Lantronix PremierWave 2050 devices running version 8.9.0.0R4 in QEMU environments.
💻 Affected Systems
- Lantronix PremierWave 2050
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise through arbitrary file overwrite leading to remote code execution, configuration tampering, or credential theft.
Likely Case
Unauthorized file access leading to sensitive information disclosure, configuration manipulation, or denial of service through critical file corruption.
If Mitigated
Limited impact if proper network segmentation, authentication controls, and file system permissions are in place.
🎯 Exploit Status
Exploitation requires valid authentication credentials but uses simple directory traversal techniques once authenticated.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check with Lantronix for updated firmware
Vendor Advisory: https://www.lantronix.com/support/security-advisories/
Restart Required: Yes
Instructions:
1. Contact Lantronix support for latest firmware. 2. Backup current configuration. 3. Apply firmware update via Web Manager or console. 4. Reboot device. 5. Verify update applied successfully.
🔧 Temporary Workarounds
Disable Web Manager FsTFtp
allDisable the vulnerable FsTFtp functionality if not required for operations
Network Segmentation
allRestrict access to Web Manager interface to trusted networks only
🧯 If You Can't Patch
- Implement strict network access controls to limit Web Manager access to authorized IPs only
- Enforce strong authentication policies and consider multi-factor authentication
🔍 How to Verify
Check if Vulnerable:
Check device firmware version via Web Manager interface or console. If running 8.9.0.0R4, device is vulnerable.Check Version:
Check via Web Manager interface or use console command specific to Lantronix devicesVerify Fix Applied:
Verify firmware version has been updated to a version later than 8.9.0.0R4📡 Detection & Monitoring
Log Indicators:
- Unusual file access patterns in Web Manager logs
- Multiple failed authentication attempts followed by successful login and file operations
Network Indicators:
- HTTP requests to Web Manager with directory traversal patterns (../ sequences)
- Unusual file transfer activity via Web Manager interface
SIEM Query:
source="lantronix_web_manager" AND (uri="*../*" OR action="file_access")