CVE-2021-27372
📋 TL;DR
CVE-2021-27372 is a critical vulnerability in Realtek xPON RTL9601D SDK 1.9 where passwords are stored in plaintext. This allows attackers to potentially gain root access to affected devices via the built-in network monitoring tool and execute arbitrary commands. Organizations using Realtek xPON RTL9601D-based networking equipment are affected.
💻 Affected Systems
- Realtek xPON RTL9601D-based networking equipment
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers gain full root control of the device, enabling them to intercept network traffic, install persistent malware, pivot to other network segments, and potentially disrupt critical network infrastructure.
Likely Case
Attackers with network access to the device can extract plaintext credentials, gain administrative access, and execute commands to compromise the device's functionality or use it as a foothold for further attacks.
If Mitigated
With proper network segmentation, access controls, and monitoring, exploitation attempts can be detected and contained before significant damage occurs.
🎯 Exploit Status
Exploitation requires network access to the device's monitoring interface but is straightforward once access is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: SDK version 1.9.1 or later
Vendor Advisory: https://www.realtek.com/images/safe-report/RTL9601D_CVE-2021-27372.pdf
Restart Required: Yes
Instructions:
1. Contact Realtek or your device manufacturer for the patched SDK version 1.9.1 or later. 2. Apply the updated firmware to all affected devices. 3. Restart devices to activate the patch. 4. Verify that passwords are no longer stored in plaintext.
🔧 Temporary Workarounds
Disable network monitoring tool
allDisable the vulnerable built-in network monitoring tool if it is not required for operations.
Check device documentation for specific disable commands
Restrict network access
allImplement strict network access controls to limit who can reach the device's management interfaces.
Use firewall rules to restrict access to device IPs on management ports
🧯 If You Can't Patch
- Isolate affected devices in a separate network segment with strict access controls.
- Implement continuous monitoring for unusual access attempts or command execution on these devices.
🔍 How to Verify
Check if Vulnerable:
Check if the device uses Realtek xPON RTL9601D SDK version 1.9 and inspect configuration files for plaintext password storage in the network monitoring tool.Check Version:
Check device firmware version via CLI or web interface; refer to manufacturer documentation for specific commands.Verify Fix Applied:
After patching, verify that passwords are encrypted in storage and test that the network monitoring tool no longer exposes credentials.📡 Detection & Monitoring
Log Indicators:
- Unusual access to network monitoring tool logs
- Failed or successful authentication attempts from unexpected IPs
- Commands executed via the monitoring interface
Network Indicators:
- Unexpected network traffic to/from device management ports
- Suspicious connections to the device's monitoring service
SIEM Query:
Example: 'source_ip=* AND dest_ip=[device_ip] AND dest_port=[monitoring_port] AND event_type=authentication'