CVE-2026-25656
📋 TL;DR
A low-privileged user can modify configuration files in SINEC NMS User Management Component, allowing malicious DLL loading. This leads to arbitrary code execution with SYSTEM privileges. All SINEC NMS versions with UMC before V2.15.2.1 are affected.
💻 Affected Systems
- SINEC NMS User Management Component (UMC)
📦 What is this software?
Sinec Nms by Siemens
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with SYSTEM privileges, enabling complete control over the affected server, data exfiltration, and lateral movement.
Likely Case
Privilege escalation from low-privileged user to SYSTEM, followed by installation of persistent backdoors or ransomware deployment.
If Mitigated
Limited impact if proper access controls and monitoring prevent unauthorized configuration file modifications.
🎯 Exploit Status
Exploitation requires low-privileged user access; DLL hijacking is a common technique.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: V2.15.2.1
Vendor Advisory: https://cert-portal.siemens.com/productcert/html/ssa-311973.html
Restart Required: Yes
Instructions:
1. Download patch from Siemens support portal. 2. Backup configuration files. 3. Apply patch according to Siemens documentation. 4. Restart SINEC NMS services.
🔧 Temporary Workarounds
Restrict File Permissions
windowsSet strict permissions on configuration files to prevent modification by low-privileged users.
icacls "C:\Path\To\SINEC\Config" /deny Users:(W)
Remove Low-Privileged Access
allTemporarily disable or restrict low-privileged user accounts until patching.
🧯 If You Can't Patch
- Implement strict access controls to prevent low-privileged users from modifying configuration files.
- Monitor for unauthorized file modifications and DLL loading events.
🔍 How to Verify
Check if Vulnerable:
Check UMC version in SINEC NMS interface; if below V2.15.2.1, system is vulnerable.Check Version:
Check via SINEC NMS web interface or Siemens management tools.Verify Fix Applied:
Confirm UMC version is V2.15.2.1 or higher after applying patch.📡 Detection & Monitoring
Log Indicators:
- Unauthorized modifications to configuration files
- Loading of unexpected DLLs in SINEC NMS logs
Network Indicators:
- Unusual outbound connections from SINEC NMS server post-exploit
SIEM Query:
EventID=4663 OR ProcessName="sinec*" AND FilePath="*.dll" | where User not in ("SYSTEM", "Administrator")