CVE-2021-27395
📋 TL;DR
This vulnerability in SIMATIC Process Historian allows unauthenticated attackers to manipulate historical process data through an interface lacking authentication. Affected systems include SIMATIC Process Historian 2013 and earlier, 2014 before SP3 Update 6, 2019, and 2020 versions. Attackers can insert, modify, or delete critical industrial process data without credentials.
💻 Affected Systems
- SIMATIC Process Historian
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of historical process data integrity, enabling data manipulation that could hide industrial incidents, falsify production records, or disrupt forensic investigations.
Likely Case
Unauthorized data modification or deletion affecting process monitoring, reporting, and compliance records in industrial environments.
If Mitigated
Limited impact with proper network segmentation and access controls preventing unauthorized access to the vulnerable interface.
🎯 Exploit Status
Exploitation requires network access to the vulnerable interface but no authentication, making it relatively simple for attackers with access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: SIMATIC Process Historian 2014 SP3 Update 6 or later; 2020 Update 2 or later; 2019 requires migration to patched version
Vendor Advisory: https://cert-portal.siemens.com/productcert/pdf/ssa-766247.pdf
Restart Required: Yes
Instructions:
1. Download appropriate patch from Siemens support portal. 2. Apply patch according to Siemens documentation. 3. Restart the Process Historian service. 4. Verify patch installation.
🔧 Temporary Workarounds
Network Segmentation
allRestrict network access to SIMATIC Process Historian interface to only authorized systems using firewall rules.
Access Control Lists
allImplement strict network ACLs to limit which IP addresses can communicate with the vulnerable interface.
🧯 If You Can't Patch
- Isolate SIMATIC Process Historian on a dedicated network segment with strict firewall rules
- Implement network monitoring and intrusion detection for unauthorized access attempts to the interface
🔍 How to Verify
Check if Vulnerable:
Check installed version of SIMATIC Process Historian against affected versions list; test network access to the interface without authentication.Check Version:
Check version in SIMATIC Process Historian administration console or Windows Programs and FeaturesVerify Fix Applied:
Verify installed version is patched (2014 SP3 Update 6+, 2020 Update 2+, or migrated from 2019) and test that interface requires authentication.📡 Detection & Monitoring
Log Indicators:
- Unauthenticated access attempts to Process Historian interface
- Unexpected data modification events in historian logs
Network Indicators:
- Unusual traffic patterns to Process Historian port from unauthorized sources
- Data manipulation requests without authentication headers
SIEM Query:
source="process_historian" AND (event_type="data_modification" OR auth_result="failed")