CVE-2017-18046
📋 TL;DR
This is a critical buffer overflow vulnerability in Dasan GPON ONT WiFi routers that allows remote attackers to execute arbitrary code by sending a specially crafted long POST request to the login_action.cgi endpoint. Attackers can gain complete control of affected routers without authentication. All users of the specified Dasan GPON ONT WiFi router models with vulnerable firmware versions are affected.
💻 Affected Systems
- Dasan GPON ONT WiFi Router H640X
📦 What is this software?
H640x Firmware by Dasannetworks
H640x Firmware by Dasannetworks
H640x Firmware by Dasannetworks
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the router allowing attackers to intercept all network traffic, install persistent malware, pivot to internal networks, and use the device as part of a botnet.
Likely Case
Router takeover leading to credential theft, man-in-the-middle attacks, DNS hijacking, and network disruption.
If Mitigated
Limited impact if routers are behind firewalls with strict ingress filtering and network segmentation.
🎯 Exploit Status
Exploit code is publicly available and requires minimal technical skill to execute. The vulnerability can be exploited remotely without authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No official vendor advisory found
Restart Required: No
Instructions:
No official patch available. Check with Dasan Networks for firmware updates. If unavailable, implement workarounds and consider device replacement.
🔧 Temporary Workarounds
Disable Remote Management
allDisable remote administration/management features to prevent external exploitation
Router-specific: Access web interface > Administration > Remote Management > Disable
Network Segmentation
allPlace routers in isolated network segments with strict firewall rules
Firewall rule: Deny external access to port 80/443 on router IPs
🧯 If You Can't Patch
- Replace affected routers with newer models from different vendors
- Implement strict network monitoring and intrusion detection for router compromise indicators
🔍 How to Verify
Check if Vulnerable:
Check router firmware version via web interface (typically under Status or System Information)Check Version:
Router-specific: Access web interface and navigate to firmware/version information pageVerify Fix Applied:
No official fix available to verify. Monitor for firmware updates from vendor.📡 Detection & Monitoring
Log Indicators:
- Unusually long POST requests to /cgi-bin/login_action.cgi
- Multiple failed login attempts followed by successful exploitation
Network Indicators:
- External IPs accessing router web interface on unusual ports
- Outbound connections from router to suspicious IPs
SIEM Query:
source_ip=external AND dest_port=80 AND uri_path="/cgi-bin/login_action.cgi" AND http_method=POST AND content_length>1000