CVE-2021-21887
📋 TL;DR
This vulnerability allows authenticated remote attackers to execute arbitrary code on Lantronix PremierWave 2050 devices by exploiting a stack-based buffer overflow in the Web Manager's SSL certificate generation functionality. Organizations using affected versions of this industrial networking hardware are at risk of complete system compromise.
💻 Affected Systems
- Lantronix PremierWave 2050
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise leading to persistent backdoor installation, data exfiltration, and use as pivot point into industrial control networks.
Likely Case
Remote code execution allowing attacker to modify device configuration, intercept network traffic, or disrupt industrial operations.
If Mitigated
Limited impact if network segmentation prevents access to management interface and authentication is properly secured.
🎯 Exploit Status
Exploit requires authentication but detailed technical analysis and proof-of-concept are publicly available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check with Lantronix for specific patched version
Vendor Advisory: https://www.lantronix.com/support/security-advisories/
Restart Required: Yes
Instructions:
1. Contact Lantronix support for firmware update. 2. Backup device configuration. 3. Apply firmware update via Web Manager or console. 4. Reboot device. 5. Verify version update.
🔧 Temporary Workarounds
Disable Web Manager Interface
linuxTemporarily disable the vulnerable Web Manager service
ssh admin@device-ip "service webmanager stop"
Network Segmentation
linuxRestrict access to management interface using firewall rules
iptables -A INPUT -p tcp --dport 80 -s trusted-network -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s trusted-network -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation to isolate PremierWave devices from untrusted networks
- Enforce strong authentication policies and monitor for unauthorized access attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version via Web Manager interface or SSH: cat /etc/versionCheck Version:
cat /etc/version || ssh admin@device-ip "cat /etc/version"Verify Fix Applied:
Verify firmware version is updated beyond 8.9.0.0R4 and test SSL certificate generation functionality📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login and SSL CSR generation requests
- Unusual process execution or network connections from device
Network Indicators:
- HTTP POST requests to /cgi-bin/sslcert with unusually large parameters
- Outbound connections from device to unexpected destinations
SIEM Query:
source="premierwave-logs" AND (url="/cgi-bin/sslcert" AND method="POST" AND size>10000) OR (process="webmanager" AND action="crash")