CVE-2021-33724
📋 TL;DR
CVE-2021-33724 is an arbitrary file deletion vulnerability in Siemens SINEC NMS that allows attackers to delete files or directories at user-controlled paths. This affects all SINEC NMS versions before V1.0 SP2 Update 1. Attackers could potentially delete critical system files, leading to service disruption or system compromise.
💻 Affected Systems
- Siemens SINEC NMS
📦 What is this software?
Sinec Nms by Siemens
Sinec Nms by Siemens
Sinec Nms by Siemens
Sinec Nms by Siemens
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise through deletion of critical operating system files, leading to permanent system damage, data loss, and extended downtime.
Likely Case
Service disruption through deletion of configuration files, application files, or log files, causing system instability and operational impact.
If Mitigated
Limited impact if proper access controls and file permissions are in place, potentially only affecting non-critical user files.
🎯 Exploit Status
Exploitation requires authentication to the SINEC NMS web interface. The vulnerability is in path traversal/file deletion functionality.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: V1.0 SP2 Update 1 or later
Vendor Advisory: https://cert-portal.siemens.com/productcert/pdf/ssa-163251.pdf
Restart Required: Yes
Instructions:
1. Download SINEC NMS V1.0 SP2 Update 1 or later from Siemens support portal. 2. Backup current configuration and data. 3. Install the update following Siemens installation guide. 4. Restart the SINEC NMS service/system.
🔧 Temporary Workarounds
Restrict Network Access
allLimit access to SINEC NMS web interface to trusted networks only using firewall rules.
Implement Strong Authentication
allEnforce strong password policies and consider multi-factor authentication for SINEC NMS access.
🧯 If You Can't Patch
- Isolate SINEC NMS system on separate network segment with strict firewall rules
- Implement file integrity monitoring to detect unauthorized file deletions
🔍 How to Verify
Check if Vulnerable:
Check SINEC NMS version in web interface under Help > About or system information page.Check Version:
Not applicable - check via web interface or Windows Control Panel > Programs and FeaturesVerify Fix Applied:
Verify version is V1.0 SP2 Update 1 or later and test file deletion functionality with path traversal attempts.📡 Detection & Monitoring
Log Indicators:
- Unusual file deletion events in SINEC NMS logs
- Multiple failed authentication attempts followed by file operations
- Path traversal patterns in web request logs
Network Indicators:
- Unusual HTTP requests to file deletion endpoints
- Requests with '../' patterns in URLs
SIEM Query:
source="sinec_nms" AND (event_type="file_delete" OR url="*../*")