CVE-2025-40937
📋 TL;DR
This vulnerability in SIMATIC CN 4100 allows authenticated attackers to execute arbitrary code with limited privileges due to improper input validation in the REST API. It affects all versions before V4.0.1 of Siemens SIMATIC CN 4100 industrial communication devices. Attackers need network access and valid credentials to exploit this vulnerability.
💻 Affected Systems
- Siemens SIMATIC CN 4100
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
An authenticated attacker could execute arbitrary code on the device, potentially gaining persistent access, disrupting industrial operations, or moving laterally within the OT network.
Likely Case
An attacker with valid credentials could execute limited code to disrupt communication services, modify configurations, or establish persistence for future attacks.
If Mitigated
With proper network segmentation and authentication controls, the impact is limited to the affected device only, preventing lateral movement.
🎯 Exploit Status
Exploitation requires authentication but the vulnerability is in a commonly attacked component (REST API). No public exploit code is currently available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: V4.0.1
Vendor Advisory: https://cert-portal.siemens.com/productcert/html/ssa-416652.html
Restart Required: Yes
Instructions:
1. Download V4.0.1 firmware from Siemens support portal. 2. Backup current configuration. 3. Apply firmware update following Siemens documentation. 4. Verify successful update and restore configuration if needed.
🔧 Temporary Workarounds
Network Segmentation
allIsolate SIMATIC CN 4100 devices in separate network segments with strict firewall rules limiting access to authorized systems only.
Authentication Hardening
allImplement strong authentication policies, multi-factor authentication where possible, and regularly rotate credentials.
🧯 If You Can't Patch
- Implement strict network access controls to limit which systems can communicate with the CN 4100 REST API
- Monitor for unusual API requests and implement rate limiting on the REST API interface
🔍 How to Verify
Check if Vulnerable:
Check device firmware version via web interface or CLI. If version is below V4.0.1, device is vulnerable.Check Version:
Check via web interface at https://<device-ip>/ or consult Siemens documentation for CLI commandsVerify Fix Applied:
After patching, verify firmware version shows V4.0.1 or higher in device management interface.📡 Detection & Monitoring
Log Indicators:
- Unusual REST API requests with unexpected parameters
- Multiple failed authentication attempts followed by successful login
- Unusual process execution or configuration changes
Network Indicators:
- Unusual traffic patterns to CN 4100 REST API endpoints
- Requests containing unexpected or malformed parameters
SIEM Query:
source="cn4100" AND (event_type="api_request" AND parameter_count>normal) OR (process_execution AND parent_process="rest_api")