CVE-2020-3409
📋 TL;DR
This vulnerability allows an unauthenticated attacker on the same network segment to send specially crafted PROFINET packets to Cisco IOS/IOS XE devices, causing them to crash and reload. This results in a denial of service affecting industrial control systems and network infrastructure. Only devices with PROFINET feature enabled are affected.
💻 Affected Systems
- Cisco IOS Software
- Cisco IOS XE Software
📦 What is this software?
Ios by Cisco
Ios by Cisco
Ios Xe by Cisco
Cisco IOS XE is Cisco's modern network operating system running on enterprise routers, switches, and wireless controllers deployed across corporate networks, data centers, branch offices, and service provider infrastructure worldwide. As the evolution of Cisco IOS, IOS XE provides a Linux-based modu...
Learn more about Ios Xe →Ios Xe by Cisco
Cisco IOS XE is Cisco's modern network operating system running on enterprise routers, switches, and wireless controllers deployed across corporate networks, data centers, branch offices, and service provider infrastructure worldwide. As the evolution of Cisco IOS, IOS XE provides a Linux-based modu...
Learn more about Ios Xe →⚠️ Risk & Real-World Impact
Worst Case
Complete device outage requiring manual reboot, disrupting industrial operations and network connectivity for extended periods.
Likely Case
Temporary service disruption during device reload, causing brief network downtime in affected segments.
If Mitigated
No impact if PROFINET is disabled or devices are properly segmented from untrusted networks.
🎯 Exploit Status
Exploitation requires network adjacency and PROFINET packets, making it accessible to attackers with basic networking knowledge.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Multiple fixed releases - refer to Cisco advisory for specific versions
Vendor Advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-profinet-J9QMCHPB
Restart Required: Yes
Instructions:
1. Check Cisco advisory for fixed software versions. 2. Download appropriate IOS/IOS XE image. 3. Backup configuration. 4. Upgrade device following Cisco upgrade procedures. 5. Verify new version is running.
🔧 Temporary Workarounds
Disable PROFINET feature
allIf PROFINET functionality is not required, disable it to eliminate the vulnerability.
no profinet
Network segmentation
allIsolate PROFINET-enabled devices from untrusted networks using VLANs or physical separation.
🧯 If You Can't Patch
- Implement strict network access controls to limit PROFINET traffic to trusted sources only
- Deploy intrusion detection systems to monitor for anomalous PROFINET traffic patterns
🔍 How to Verify
Check if Vulnerable:
Check if device has PROFINET enabled: 'show running-config | include profinet' and compare IOS/IOS XE version against Cisco advisory.Check Version:
show versionVerify Fix Applied:
Verify upgraded version matches fixed releases in Cisco advisory and PROFINET is either disabled or patched version is running.📡 Detection & Monitoring
Log Indicators:
- Device crash logs
- Unexpected reload messages
- PROFINET protocol errors in system logs
Network Indicators:
- Unusual PROFINET traffic patterns
- PROFINET packets from unexpected sources
- Sudden device unavailability
SIEM Query:
source="network_device" ("reload" OR "crash") AND "PROFINET"