CVE-2017-7175
📋 TL;DR
CVE-2017-7175 is a critical command injection vulnerability in NfSen network flow analysis software. Attackers can execute arbitrary operating system commands by injecting shell metacharacters into the 'customfmt' parameter. This affects all NfSen installations before version 1.3.8.
💻 Affected Systems
- NfSen
📦 What is this software?
Nfsen by Nfsen
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to execute arbitrary commands with web server privileges, potentially leading to data theft, lateral movement, or ransomware deployment.
Likely Case
Remote code execution leading to unauthorized access, data exfiltration, or installation of backdoors on vulnerable NfSen servers.
If Mitigated
Limited impact if proper network segmentation, least privilege, and input validation are implemented, though exploitation risk remains.
🎯 Exploit Status
Public exploit code available on Exploit-DB (ID: 42314), making exploitation trivial for attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.3.8
Vendor Advisory: https://sourceforge.net/p/nfsen/news/2017/01/nfsen-138-released---security-fix/
Restart Required: Yes
Instructions:
1. Download NfSen 1.3.8 from official source. 2. Backup current configuration. 3. Stop NfSen service. 4. Install new version following upgrade instructions. 5. Restart NfSen service.
🔧 Temporary Workarounds
Input Validation Filter
linuxAdd input validation to reject shell metacharacters in customfmt parameter
Modify NfSen source to sanitize customfmt input before processing
Web Application Firewall
allDeploy WAF rules to block command injection patterns
🧯 If You Can't Patch
- Network segmentation: Isolate NfSen server from critical systems
- Implement strict firewall rules to limit access to NfSen web interface
🔍 How to Verify
Check if Vulnerable:
Check NfSen version via web interface or configuration files; versions <1.3.8 are vulnerableCheck Version:
grep 'version' /path/to/nfsen/conf/nfsen.conf or check web interfaceVerify Fix Applied:
Verify version is 1.3.8 or later and test customfmt parameter with shell metacharacters (safely in test environment)📡 Detection & Monitoring
Log Indicators:
- Unusual command execution in web server logs
- Suspicious strings in customfmt parameter requests
- Shell metacharacters in HTTP parameters
Network Indicators:
- Unexpected outbound connections from NfSen server
- Suspicious payloads in HTTP requests to NfSen
SIEM Query:
web.url:*customfmt* AND (web.param:*;* OR web.param:*|* OR web.param:*`* OR web.param:*$(*)