CVE-2020-27859
📋 TL;DR
CVE-2020-27859 is an unauthenticated path traversal vulnerability in NEC ESMPRO Manager that allows remote attackers to read arbitrary files on the system. The vulnerability exists in the GetEuaLogDownloadAction class where user-supplied paths aren't properly validated before file operations. Organizations using NEC ESMPRO Manager for server management are affected.
💻 Affected Systems
- NEC ESMPRO Manager
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers could read sensitive system files, configuration files, credentials, or other critical data, potentially leading to full system compromise.
Likely Case
Information disclosure of sensitive files, potentially including system logs, configuration files, or other data accessible to the SYSTEM account.
If Mitigated
Limited impact if network access is restricted and proper file permissions are in place.
🎯 Exploit Status
ZDI-CAN-9607 indicates this was reported through coordinated disclosure. The vulnerability requires no authentication and has straightforward exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 6.43 or later
Vendor Advisory: https://www.nec.com/en/global/prod/express5800/software/esmpro.html
Restart Required: Yes
Instructions:
1. Download the latest NEC ESMPRO Manager version from NEC's official website. 2. Backup current configuration. 3. Install the update following NEC's installation guide. 4. Restart the ESMPRO Manager service.
🔧 Temporary Workarounds
Network Access Restriction
windowsRestrict network access to ESMPRO Manager to trusted IP addresses only
Use Windows Firewall: New-NetFirewallRule -DisplayName "Block ESMPRO" -Direction Inbound -Protocol TCP -LocalPort 80,443 -RemoteAddress NotTrustedIPs -Action Block
🧯 If You Can't Patch
- Implement strict network segmentation to isolate ESMPRO Manager from untrusted networks
- Monitor for unusual file access patterns and implement file integrity monitoring
🔍 How to Verify
Check if Vulnerable:
Check ESMPRO Manager version in the application interface or registry: HKEY_LOCAL_MACHINE\SOFTWARE\NEC\ESMPRO Manager\VersionCheck Version:
reg query "HKLM\SOFTWARE\NEC\ESMPRO Manager" /v VersionVerify Fix Applied:
Verify version is 6.43 or higher and test the GetEuaLogDownloadAction functionality with path traversal attempts📡 Detection & Monitoring
Log Indicators:
- Unusual file access patterns in ESMPRO logs
- Multiple failed path traversal attempts
- Access to system files through ESMPRO interface
Network Indicators:
- HTTP requests to ESMPRO with path traversal patterns (../ sequences)
- Unusual file download requests from ESMPRO endpoints
SIEM Query:
source="esmpro.log" AND ("../" OR "..\\" OR "%2e%2e%2f")