CVE-2021-32928
📋 TL;DR
This vulnerability in Sentinel LDK Run-Time Environment installer versions 7.6 and prior leaves TCP Port 1947 open after uninstallation, allowing unauthorized incoming connections from private networks. It affects systems where the software was installed and then uninstalled, potentially exposing them to remote attacks.
💻 Affected Systems
- Sentinel LDK Run-Time Environment
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers could exploit the open port to gain unauthorized access, execute arbitrary code, or compromise the system, leading to data theft, ransomware deployment, or network pivoting.
Likely Case
Malicious actors scanning for open ports could discover and exploit this to install malware, exfiltrate data, or use the system as a foothold for further attacks within the network.
If Mitigated
With proper network segmentation and firewall rules blocking Port 1947, the risk is reduced to minimal, though residual exposure may exist if other vulnerabilities are present.
🎯 Exploit Status
Exploitation is straightforward as it involves connecting to an open port, but specific exploit details are not publicly documented.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 7.7 or later
Vendor Advisory: https://us-cert.cisa.gov/ics/advisories/icsa-21-159-06
Restart Required: No
Instructions:
1. Update Sentinel LDK Run-Time Environment to version 7.7 or later. 2. If uninstalling, ensure the new version properly removes the firewall rule for Port 1947.
🔧 Temporary Workarounds
Manually Remove Firewall Rule
allDelete the 'Sentinel License Manager' firewall rule to block incoming connections on Port 1947.
On Windows: netsh advfirewall firewall delete rule name="Sentinel License Manager"
On Linux: sudo iptables -D INPUT -p tcp --dport 1947 -j DROP (adjust for specific firewall)
Block Port 1947 with Firewall
allConfigure firewall to deny incoming traffic on TCP Port 1947 from private networks.
On Windows: netsh advfirewall firewall add rule name="Block Port 1947" dir=in action=block protocol=TCP localport=1947
On Linux: sudo iptables -A INPUT -p tcp --dport 1947 -j DROP
🧯 If You Can't Patch
- Implement network segmentation to isolate affected systems and restrict access to Port 1947.
- Monitor network traffic on Port 1947 for suspicious activity and use intrusion detection systems.
🔍 How to Verify
Check if Vulnerable:
Check if Port 1947 is open and listening on the system, especially after uninstalling Sentinel LDK. Use commands like 'netstat -an | findstr :1947' on Windows or 'ss -tlnp | grep :1947' on Linux.Check Version:
On Windows: Check program version in Control Panel or run installer with version flag. On Linux: Check package version with command like 'rpm -qa | grep sentinel' or 'dpkg -l | grep sentinel'.Verify Fix Applied:
After updating or applying workarounds, verify Port 1947 is closed by running the same check commands and ensuring no listening service is present.📡 Detection & Monitoring
Log Indicators:
- Firewall logs showing rule changes for 'Sentinel License Manager'
- System logs indicating uninstallation events of Sentinel LDK
Network Indicators:
- Unexpected incoming connections to TCP Port 1947 from private network addresses
- Network scans targeting Port 1947
SIEM Query:
Example: source="firewall" AND rule_name="Sentinel License Manager" OR destination_port=1947