CVE-2020-29381
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary commands on affected V-SOL OLT devices by injecting malicious commands into filenames during TFTP upload operations. Attackers can achieve full system compromise with root privileges. All users of specified V-SOL OLT models with vulnerable firmware versions are affected.
💻 Affected Systems
- V-SOL V1600D
- V1600D4L
- V1600D-MINI
- V1600G1
- V1600G2
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system takeover allowing installation of persistent backdoors, credential theft, network pivoting, and device bricking.
Likely Case
Unauthenticated remote code execution leading to configuration manipulation, data exfiltration, and denial of service.
If Mitigated
Limited impact if devices are isolated in management VLANs with strict network controls and command filtering.
🎯 Exploit Status
Exploit requires CLI access but no authentication. Simple command injection via filename parameter.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not publicly available
Restart Required: No
Instructions:
Contact V-SOL vendor for firmware updates. No official patch information is publicly documented.
🔧 Temporary Workarounds
Disable TFTP upload functionality
allRemove or restrict access to TFTP upload commands in CLI
no upload tftp syslog
no upload tftp configuration
Implement input validation
allAdd filename validation to reject special characters
Configure filename filtering to reject ; & | $ ( ) characters
🧯 If You Can't Patch
- Isolate devices in management VLAN with strict ACLs
- Implement network monitoring for TFTP traffic to/from affected devices
🔍 How to Verify
Check if Vulnerable:
Check firmware version via CLI: show version. If version matches affected list and TFTP upload is enabled, device is vulnerable.Check Version:
show versionVerify Fix Applied:
Test command injection by attempting to upload file with malicious filename containing command characters.📡 Detection & Monitoring
Log Indicators:
- TFTP upload attempts with unusual filenames
- CLI commands containing special characters in upload operations
Network Indicators:
- TFTP traffic to/from OLT devices on port 69
- Unexpected outbound connections from OLT devices
SIEM Query:
source_port:69 AND (filename:*;* OR filename:*&* OR filename:*|* OR filename:*$* OR filename:*(* OR filename:*)*)