CVE-2021-27388
📋 TL;DR
This vulnerability in Siemens SINAMICS medium voltage products allows unauthenticated attackers to cause denial-of-service, execute limited configuration changes, and run limited control commands via the Sm@rtServer remote access component. It affects all versions of SINAMICS SL150, SM150, and SM150i medium voltage products. The CVSS 9.8 score indicates critical severity.
💻 Affected Systems
- SINAMICS SL150
- SINAMICS SM150
- SINAMICS SM150i
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system shutdown of industrial medium voltage drives, potentially causing production stoppage, equipment damage, or safety incidents in critical infrastructure.
Likely Case
Denial-of-service causing operational disruption and limited unauthorized configuration changes to industrial control systems.
If Mitigated
Minimal impact if systems are properly segmented, access controlled, and monitored with network security controls.
🎯 Exploit Status
Unauthenticated access lowers exploitation barrier. Industrial control system vulnerabilities often attract targeted attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Contact Siemens for specific firmware updates
Vendor Advisory: https://us-cert.cisa.gov/ics/advisories/icsa-21-131-04
Restart Required: Yes
Instructions:
1. Contact Siemens Industrial Customer Support for firmware updates. 2. Apply firmware updates following Siemens documentation. 3. Restart affected systems after patching. 4. Verify functionality post-update.
🔧 Temporary Workarounds
Network Segmentation
allIsolate SINAMICS products in dedicated network segments with strict access controls.
Disable Sm@rtServer
allDisable remote access via Sm@rtServer if not required for operations.
🧯 If You Can't Patch
- Implement strict network segmentation and firewall rules to limit access to SINAMICS products
- Deploy intrusion detection systems monitoring for anomalous access to industrial control systems
🔍 How to Verify
Check if Vulnerable:
Check if SINAMICS SL150/SM150/SM150i products with Sm@rtServer enabled are deployed in your environment.Check Version:
Check firmware version via Siemens SINAMICS interface or contact Siemens supportVerify Fix Applied:
Verify with Siemens that firmware has been updated to a version addressing CVE-2021-27388.📡 Detection & Monitoring
Log Indicators:
- Unauthenticated access attempts to Sm@rtServer
- Unexpected configuration changes
- Denial-of-service events on SINAMICS systems
Network Indicators:
- Unusual traffic to SINAMICS management ports
- Traffic patterns indicating exploitation attempts
SIEM Query:
source_ip=* AND dest_port=(Sm@rtServer_port) AND auth_failure=true