CVE-2020-16839 – This vulnerability allows unauthenticated attac... (How to Fix)

Q: What is the severity of CVE-2020-16839?

CVE-2020-16839 has a CVSS score of 7.5 (HIGH). This vulnerability allows unauthenticated attackers to change passwords on Crestron DM-NVX devices via WebSocket requests. It affects Crestron DM-NVX-DIR, DM-NVX-DIR80, and DM-NVX-ENT devices before firmware patch DM-XIO/1-0-3-802. Organizations using these devices for AV/IT systems are at risk.

📋 TL;DR

This vulnerability allows unauthenticated attackers to change passwords on Crestron DM-NVX devices via WebSocket requests. It affects Crestron DM-NVX-DIR, DM-NVX-DIR80, and DM-NVX-ENT devices before firmware patch DM-XIO/1-0-3-802. Organizations using these devices for AV/IT systems are at risk.

💻 Affected Systems

Products:

Crestron DM-NVX-DIR
Crestron DM-NVX-DIR80
Crestron DM-NVX-ENT

Versions: All versions before DM-XIO/1-0-3-802

Operating Systems: Embedded Crestron OS

Default Config Vulnerable: ⚠️ Yes

Notes: Devices must have WebSocket interface enabled (default). Network accessibility required.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete device takeover allowing attackers to reconfigure systems, intercept AV streams, pivot to internal networks, or deploy ransomware on connected systems.

🟠

Likely Case

Unauthorized password changes leading to device lockout, service disruption, or credential harvesting for further attacks.

🟢

If Mitigated

Limited impact with proper network segmentation and monitoring, though authentication bypass remains possible.

🌐 Internet-Facing: HIGH - WebSocket interface accessible from network allows remote exploitation without authentication.

🏢 Internal Only: HIGH - Even internally, any network-accessible device can be exploited by compromised internal hosts.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Simple WebSocket request manipulation required. No authentication needed.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: DM-XIO/1-0-3-802

Vendor Advisory: https://www.crestron.com/Software-Firmware/Firmware/DigitalMedia/DM-XIO/1-0-3-802

Restart Required: Yes

Instructions:

1. Download DM-XIO/1-0-3-802 firmware from Crestron support site. 2. Upload firmware to device via web interface. 3. Apply update. 4. Reboot device. 5. Verify firmware version.

🔧 Temporary Workarounds

Network Segmentation

all

Isolate Crestron devices on separate VLAN with strict firewall rules.

WebSocket Interface Restriction

all

Block WebSocket traffic (port 80/443) to devices except from management systems.

🧯 If You Can't Patch

Segment network: Place devices on isolated VLAN with strict access controls.
Monitor logs: Alert on WebSocket authentication attempts and password change events.

🔍 How to Verify

Check if Vulnerable:

Check firmware version via web interface: Settings > System Information. If version is below DM-XIO/1-0-3-802, device is vulnerable.

Check Version:

Via web interface navigation or Crestron Toolbox software connection.

Verify Fix Applied:

Confirm firmware version shows DM-XIO/1-0-3-802 or higher in System Information.

📡 Detection & Monitoring

Log Indicators:

WebSocket connection attempts from unauthorized IPs
Password change events without prior authentication
Failed authentication followed by successful WebSocket request

Network Indicators:

WebSocket traffic to device ports 80/443 from unexpected sources
Unusual pattern of WebSocket handshake requests

SIEM Query:

source="crestron_device" AND (event_type="password_change" OR protocol="websocket") AND NOT user="authenticated"

📊 Metadata

CVE ID: CVE-2020-16839

CVSS v3 Score: 7.5 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CWE: CWE-287

Published: July 30, 2021

Last Updated: November 21, 2024

🔗 References

https://support.crestron.com Vendor Advisory
https://www.crestron.com/Software-Firmware/Firmware/DigitalMedia/DM-XIO/1-0-3-802 Permissions Required
https://www.security.crestron.com Broken Link
https://www.crestron.com/Security/Security-at-Crestron Vendor Advisory
https://support.crestron.com Vendor Advisory
https://www.crestron.com/Software-Firmware/Firmware/DigitalMedia/DM-XIO/1-0-3-802 Permissions Required
https://www.security.crestron.com Broken Link

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