CVE-2021-40368
📋 TL;DR
This vulnerability affects multiple Siemens SIMATIC S7-400 and S7-410 industrial controllers. An attacker can send specially crafted packets to TCP port 102 to cause a denial-of-service condition, requiring a device restart to recover. Organizations using these industrial control systems in critical infrastructure are affected.
💻 Affected Systems
- SIMATIC S7-400 CPU 412-1 DP V7
- SIMATIC S7-400 CPU 412-2 DP V7
- SIMATIC S7-400 CPU 412-2 PN/DP V7
- SIMATIC S7-400 CPU 414-2 DP V7
- SIMATIC S7-400 CPU 414-3 DP V7
- SIMATIC S7-400 CPU 414-3 PN/DP V7
- SIMATIC S7-400 CPU 414F-3 PN/DP V7
- SIMATIC S7-400 CPU 416-2 DP V7
- SIMATIC S7-400 CPU 416-3 DP V7
- SIMATIC S7-400 CPU 416-3 PN/DP V7
- SIMATIC S7-400 CPU 416F-2 DP V7
- SIMATIC S7-400 CPU 416F-3 PN/DP V7
- SIMATIC S7-400 CPU 417-4 DP V7
- SIMATIC S7-400 H V6 CPU family
- SIMATIC S7-410 V10 CPU family
- SIMATIC S7-410 V8 CPU family
- SIPLUS S7-400 CPU 414-3 PN/DP V7
- SIPLUS S7-400 CPU 416-3 PN/DP V7
- SIPLUS S7-400 CPU 416-3 V7
- SIPLUS S7-400 CPU 417-4 V7
📦 What is this software?
Simatic S7 400 Pn\/dp V7 Firmware by Siemens
⚠️ Risk & Real-World Impact
Worst Case
Critical industrial processes are disrupted, causing production downtime, safety hazards, or environmental impacts in manufacturing, energy, or water treatment facilities.
Likely Case
Temporary disruption of industrial automation processes requiring manual intervention and system restart, causing production delays.
If Mitigated
Isolated impact on single controller with redundant systems maintaining operations while affected device is restarted.
🎯 Exploit Status
Exploitation requires network access to port 102/tcp but no authentication. Crafted packets can be sent remotely.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: V7.0.3 for PN/DP models, V6.0.10 for H family, V10.1 for V10 family, V8.2.3 for V8 family
Vendor Advisory: https://cert-portal.siemens.com/productcert/pdf/ssa-557541.pdf
Restart Required: Yes
Instructions:
1. Download firmware updates from Siemens Industry Online Support
2. Backup current configuration and program
3. Update firmware using appropriate Siemens tools (TIA Portal, STEP 7)
4. Restart the CPU
5. Verify functionality and restore configuration if needed
🔧 Temporary Workarounds
Network segmentation and firewall rules
allRestrict access to port 102/tcp to only authorized engineering stations and trusted networks
Disable unnecessary services
allIf ISO-TSAP service on port 102 is not required, disable it in controller configuration
🧯 If You Can't Patch
- Implement strict network segmentation with industrial firewalls to isolate controllers from untrusted networks
- Deploy intrusion detection systems monitoring for anomalous traffic patterns on port 102/tcp
🔍 How to Verify
Check if Vulnerable:
Check CPU firmware version in TIA Portal or STEP 7 project, or via web interface if available. Compare against affected versions list.Check Version:
Not applicable - check via Siemens engineering software or controller displayVerify Fix Applied:
Confirm firmware version is updated to patched versions: V7.0.3+ for PN/DP models, V6.0.10+ for H family, V10.1+ for V10 family, V8.2.3+ for V8 family.📡 Detection & Monitoring
Log Indicators:
- CPU going to STOP mode unexpectedly
- Communication errors on port 102
- Controller restart events
Network Indicators:
- Unusual traffic patterns to port 102/tcp
- Malformed packets to port 102
- Connection attempts from unauthorized sources
SIEM Query:
source_port:102 AND (packet_size:anomalous OR protocol_violation:true)