CVE-2021-26637
📋 TL;DR
CVE-2021-26637 allows unauthenticated remote attackers to fully control SiHAS SGW-300, ACM-300, and GCM-300 devices due to missing authentication and permission checks in firmware and applications. This affects all users of these industrial control devices who haven't implemented compensating controls.
💻 Affected Systems
- SiHAS SGW-300
- SiHAS ACM-300
- SiHAS GCM-300
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device takeover allowing attackers to manipulate industrial processes, disrupt operations, or use devices as footholds into industrial control networks.
Likely Case
Unauthorized configuration changes, service disruption, or device compromise leading to operational impact.
If Mitigated
Limited impact if devices are isolated behind firewalls with strict network access controls.
🎯 Exploit Status
Exploitation requires only network access to device management interfaces.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check with SiHAS for specific patched firmware versions
Vendor Advisory: https://www.krcert.or.kr/krcert/secNoticeView.do?bulletin_writing_sequence=66782
Restart Required: Yes
Instructions:
1. Contact SiHAS for patched firmware. 2. Backup device configuration. 3. Apply firmware update via management interface. 4. Verify authentication is now required.
🔧 Temporary Workarounds
Network Segmentation
allIsolate devices in separate VLAN with strict firewall rules
Access Control Lists
allImplement IP-based restrictions to limit management access
🧯 If You Can't Patch
- Deploy network-based intrusion detection to monitor for unauthorized access attempts
- Implement physical access controls and air-gap devices where possible
🔍 How to Verify
Check if Vulnerable:
Attempt to access device management interface without credentials. If access is granted, device is vulnerable.Check Version:
Check device web interface or console for firmware version informationVerify Fix Applied:
Verify authentication is now required for all management functions and test with invalid credentials.📡 Detection & Monitoring
Log Indicators:
- Unauthenticated access to management endpoints
- Configuration changes without authentication events
Network Indicators:
- Unusual management traffic from unauthorized IPs
- Protocol anomalies in device communications
SIEM Query:
source_ip NOT IN authorized_management_ips AND destination_port IN [device_management_ports]