CVE-2015-6016
📋 TL;DR
This vulnerability allows remote attackers to gain administrative access to affected ZyXEL networking devices by using the default password '1234' for the admin account. It affects ZyXEL P-660HW-T1 2, PMG5318-B20A, and NBG-418N devices with specific firmware versions. Attackers can take full control of these devices without authentication.
💻 Affected Systems
- ZyXEL P-660HW-T1 2
- ZyXEL PMG5318-B20A
- ZyXEL NBG-418N
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attackers to reconfigure network settings, intercept traffic, install malware, or use the device as a pivot point into internal networks.
Likely Case
Unauthorized administrative access leading to network configuration changes, DNS hijacking, or device takeover for botnet participation.
If Mitigated
Limited impact if devices are behind firewalls, not internet-facing, and have proper network segmentation.
🎯 Exploit Status
Exploitation requires only knowledge of the default password and network access to the device.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not available
Vendor Advisory: https://www.kb.cert.org/vuls/id/870744
Restart Required: No
Instructions:
1. Log into device admin interface
2. Navigate to administration/user settings
3. Change default password '1234' to a strong, unique password
4. Save configuration changes
🔧 Temporary Workarounds
Change Default Password
allImmediately change the admin password from default '1234' to a strong, unique password.
Network Segmentation
allIsolate affected devices in separate VLANs or network segments to limit attack surface.
🧯 If You Can't Patch
- Disable remote administration and restrict management access to trusted internal IPs only
- Replace affected devices with newer models that don't have this vulnerability
🔍 How to Verify
Check if Vulnerable:
Attempt to log into device admin interface using username 'admin' and password '1234'Check Version:
Check device web interface or console for firmware version informationVerify Fix Applied:
Verify you cannot log in with default credentials and only your new strong password works📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts followed by successful admin login
- Configuration changes from unknown IP addresses
Network Indicators:
- Unexpected administrative access from external IPs
- Unusual traffic patterns from affected devices
SIEM Query:
source="router_logs" (login="admin" AND password="1234") OR (user="admin" AND result="success" AND source_ip NOT IN trusted_ips)🔗 References
- http://www.securitytracker.com/id/1034552
- http://www.securitytracker.com/id/1034553
- http://www.securitytracker.com/id/1034554
- https://www.kb.cert.org/vuls/id/870744
- https://www.kb.cert.org/vuls/id/BLUU-9ZQU2R
- http://www.securitytracker.com/id/1034552
- http://www.securitytracker.com/id/1034553
- http://www.securitytracker.com/id/1034554
- https://www.kb.cert.org/vuls/id/870744
- https://www.kb.cert.org/vuls/id/BLUU-9ZQU2R
