CVE-2025-4076
📋 TL;DR
This critical vulnerability in LB-LINK BL-AC3600 routers allows remote attackers to execute arbitrary commands via command injection in the password handler. Attackers can exploit this to take control of affected devices. All users of LB-LINK BL-AC3600 routers up to version 1.0.22 are affected.
💻 Affected Systems
- LB-LINK BL-AC3600
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attackers to install persistent backdoors, intercept network traffic, pivot to internal networks, or use the device for botnet activities.
Likely Case
Remote code execution leading to device takeover, credential theft, and network surveillance capabilities.
If Mitigated
Limited impact if devices are behind firewalls with strict inbound filtering and network segmentation.
🎯 Exploit Status
Public proof-of-concept exploit available on GitHub. Attack requires network access to the router's web interface.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: None available
Restart Required: No
Instructions:
No official patch available. Vendor has not responded to disclosure. Consider replacing affected devices with supported alternatives.
🔧 Temporary Workarounds
Disable Remote Management
allDisable web interface access from WAN/Internet to prevent remote exploitation
Network Segmentation
allPlace affected routers in isolated network segments with strict firewall rules
🧯 If You Can't Patch
- Replace affected devices with supported alternatives from vendors with active security response
- Implement strict network access controls to limit exposure to trusted IPs only
🔍 How to Verify
Check if Vulnerable:
Check router firmware version via web interface at http://[router-ip]/ or via SSH if availableCheck Version:
curl -s http://[router-ip]/cgi-bin/lighttpd.cgi | grep version || ssh admin@[router-ip] 'cat /etc/version'Verify Fix Applied:
No fix available to verify. Monitor for vendor updates.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /cgi-bin/lighttpd.cgi with routepwd parameter containing shell metacharacters
- Unexpected command execution in system logs
Network Indicators:
- Unusual outbound connections from router to external IPs
- Traffic patterns suggesting device compromise
SIEM Query:
source="router_logs" AND uri="/cgi-bin/lighttpd.cgi" AND (routepwd CONTAINS "|" OR routepwd CONTAINS ";" OR routepwd CONTAINS "`" OR routepwd CONTAINS "$")