CVE-2018-20438
📋 TL;DR
This vulnerability allows remote attackers to retrieve Wi-Fi credentials from Technicolor TC7110.AR routers via SNMP requests. Attackers can exploit this to gain unauthorized access to wireless networks. Affected users are those with vulnerable Technicolor router models exposed to untrusted networks.
💻 Affected Systems
- Technicolor TC7110.AR
📦 What is this software?
Tc7110.ar Firmware by Technicolor
⚠️ Risk & Real-World Impact
Worst Case
Attackers gain full access to the wireless network, intercept all traffic, perform man-in-the-middle attacks, and potentially pivot to other devices on the network.
Likely Case
Unauthorized users connect to the Wi-Fi network, consuming bandwidth and potentially accessing shared resources on the local network.
If Mitigated
With proper network segmentation and SNMP restrictions, impact is limited to isolated network segments only.
🎯 Exploit Status
Simple SNMP queries to specific OIDs (iso.3.6.1.4.1.2863.205.10.1.30.4.1.14.1.3.32 and iso.3.6.1.4.1.2863.205.10.1.30.4.2.4.1.2.32) return Wi-Fi credentials without authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Later than STD3.38.03 (specific version not publicly documented)
Vendor Advisory: Not publicly available
Restart Required: Yes
Instructions:
1. Check for firmware updates from your ISP or Technicolor. 2. Download and apply the latest firmware. 3. Reboot the router after update. 4. Verify SNMP is disabled or properly secured.
🔧 Temporary Workarounds
Disable SNMP Service
allCompletely disable SNMP on the router to prevent credential exposure.
Access router admin interface -> Advanced Settings -> SNMP -> Disable
Restrict SNMP Access
allConfigure SNMP to only allow access from trusted management IP addresses.
Access router admin interface -> Advanced Settings -> SNMP -> Set allowed IPs to management network only
🧯 If You Can't Patch
- Change Wi-Fi credentials immediately and regularly
- Isolate router management interface to separate VLAN
🔍 How to Verify
Check if Vulnerable:
Run SNMP walk command: snmpwalk -v2c -c public [router_ip] .1.3.6.1.4.1.2863.205.10.1.30.4.1.14.1.3.32Check Version:
Check router web interface or use: snmpget -v2c -c public [router_ip] .1.3.6.1.4.1.2863.205.1.1.1.0Verify Fix Applied:
Attempt the same SNMP query after remediation - should return no data or access denied.📡 Detection & Monitoring
Log Indicators:
- SNMP queries to OIDs containing .2863.205.10.1.30.4
- Multiple failed SNMP authentication attempts
Network Indicators:
- SNMP traffic from untrusted sources to router IP
- Unusual SNMP query patterns
SIEM Query:
source_ip=* AND destination_port=161 AND (oid="*.2863.205.10.1.30.4*" OR community_string="public")