CVE-2020-6989

Q: What is the severity of CVE-2020-6989?

CVE-2020-6989 has a CVSS score of 9.8 (CRITICAL). A buffer overflow vulnerability in Moxa PT-7528 and PT-7828 series industrial switches allows remote attackers to crash the web server or execute arbitrary code. This affects devices with vulnerable firmware versions exposed to network access. The high CVSS score reflects the potential for complete system compromise.

9.8 CRITICAL

📋 TL;DR

A buffer overflow vulnerability in Moxa PT-7528 and PT-7828 series industrial switches allows remote attackers to crash the web server or execute arbitrary code. This affects devices with vulnerable firmware versions exposed to network access. The high CVSS score reflects the potential for complete system compromise.

💻 Affected Systems

Products:

Moxa PT-7528 series
Moxa PT-7828 series

Versions: PT-7528: Version 4.0 or lower, PT-7828: Version 3.9 or lower

Operating Systems: Embedded firmware

Default Config Vulnerable: ⚠️ Yes

Notes: All devices with default web server configuration are vulnerable when network-accessible.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution leading to full device compromise, network disruption, and potential lateral movement within industrial control systems.

🟠

Likely Case

Denial-of-service causing device reboot and network interruption in industrial environments.

🟢

If Mitigated

Limited impact if devices are isolated behind firewalls with restricted web interface access.

🌐 Internet-Facing: HIGH

🏢 Internal Only: MEDIUM

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Buffer overflow in web server suggests straightforward exploitation once details are known.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: PT-7528: Version 4.1 or higher, PT-7828: Version 4.0 or higher

Vendor Advisory: https://www.moxa.com/en/support/product-support/security-advisory/moxa-pt-7528-pt-7828-series-web-server-buffer-overflow-vulnerability

Restart Required: Yes

Instructions:

1. Download latest firmware from Moxa support portal. 2. Backup device configuration. 3. Upload firmware via web interface. 4. Reboot device. 5. Restore configuration if needed.

🔧 Temporary Workarounds

Disable web interface

all

Disable HTTP/HTTPS web server if not required for operations

Network segmentation

all

Restrict access to web interface using firewall rules

🧯 If You Can't Patch

Isolate devices in separate VLAN with strict firewall rules
Implement network monitoring for web server access attempts

🔍 How to Verify

Check if Vulnerable:

Check firmware version via web interface at System > Maintenance > Firmware

Check Version:

No CLI command - use web interface or SNMP query

Verify Fix Applied:

Confirm firmware version is PT-7528 >= 4.1 or PT-7828 >= 4.0

📡 Detection & Monitoring

Log Indicators:

Web server crash logs
Unusual HTTP requests to web interface

Network Indicators:

HTTP requests with abnormal payload length to device IP

SIEM Query:

source_ip="device_ip" AND (http_request_size > 10000 OR http_status=500)

📊 Metadata

CVE ID: CVE-2020-6989

CVSS v3 Score: 9.8 (CRITICAL)

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

CWE: CWE-121

Published: March 24, 2020

Last Updated: November 21, 2024

🔗 References

https://www.us-cert.gov/ics/advisories/icsa-20-056-03 Third Party Advisory,US Government Resource
https://www.us-cert.gov/ics/advisories/icsa-20-056-03 Third Party Advisory,US Government Resource

📋 TL;DR

💻 Affected Systems

📦 What is this software?

Pt 7528 12msc 12tx 4gsfp Hv Firmware by Moxa

Pt 7528 12msc 12tx 4gsfp Hv Hv Firmware by Moxa

Pt 7528 12msc 12tx 4gsfp Wv Firmware by Moxa

Pt 7528 12msc 12tx 4gsfp Wv Wv Firmware by Moxa

Pt 7528 12mst 12tx 4gsfp Hv Firmware by Moxa

Pt 7528 12mst 12tx 4gsfp Hv Hv Firmware by Moxa

Pt 7528 12mst 12tx 4gsfp Wv Firmware by Moxa

Pt 7528 12mst 12tx 4gsfp Wv Wv Firmware by Moxa

Pt 7528 16msc 8tx 4gsfp Hv Firmware by Moxa

Pt 7528 16msc 8tx 4gsfp Hv Hv Firmware by Moxa

Pt 7528 16msc 8tx 4gsfp Wv Firmware by Moxa

Pt 7528 16msc 8tx 4gsfp Wv Wv Firmware by Moxa

Pt 7528 16mst 8tx 4gsfp Hv Firmware by Moxa

Pt 7528 16mst 8tx 4gsfp Hv Hv Firmware by Moxa

Pt 7528 16mst 8tx 4gsfp Wv Firmware by Moxa

Pt 7528 16mst 8tx 4gsfp Wv Wv Firmware by Moxa

Pt 7528 20msc 4tx 4gsfp Hv Firmware by Moxa

Pt 7528 20msc 4tx 4gsfp Hv Hv Firmware by Moxa

Pt 7528 20msc 4tx 4gsfp Wv Firmware by Moxa

Pt 7528 20msc 4tx 4gsfp Wv Wv Firmware by Moxa

Pt 7528 20mst 4tx 4gsfp Hv Firmware by Moxa

Pt 7528 20mst 4tx 4gsfp Hv Hv Firmware by Moxa

Pt 7528 20mst 4tx 4gsfp Wv Firmware by Moxa

Pt 7528 20mst 4tx 4gsfp Wv Wv Firmware by Moxa

Pt 7528 24tx Hv Firmware by Moxa

Pt 7528 24tx Hv Hv Firmware by Moxa

Pt 7528 24tx Wv Firmware by Moxa

Pt 7528 24tx Wv Hv Firmware by Moxa

Pt 7528 24tx Wv Wv Firmware by Moxa

Pt 7528 8msc 16tx 4gsfp Hv Firmware by Moxa

Pt 7528 8msc 16tx 4gsfp Hv Hv Firmware by Moxa

Pt 7528 8msc 16tx 4gsfp Wv Firmware by Moxa

Pt 7528 8msc 16tx 4gsfp Wv Wv Firmware by Moxa

Pt 7528 8mst 16tx 4gsfp Hv Firmware by Moxa

Pt 7528 8mst 16tx 4gsfp Hv Hv Firmware by Moxa

Pt 7528 8mst 16tx 4gsfp Wv Firmware by Moxa

Pt 7528 8mst 16tx 4gsfp Wv Wv Firmware by Moxa

Pt 7528 8ssc 16tx 4gsfp Hv Hv Firmware by Moxa

Pt 7528 8ssc 16tx 4gsfp Wv Wv Firmware by Moxa

Pt 7828 F 24 24 Firmware by Moxa

Pt 7828 F 24 Firmware by Moxa

Pt 7828 F 24 Hv Firmware by Moxa

Pt 7828 F 48 48 Firmware by Moxa

Pt 7828 F 48 Firmware by Moxa

Pt 7828 F 48 Hv Firmware by Moxa

Pt 7828 F Hv Firmware by Moxa

Pt 7828 F Hv Hv Firmware by Moxa

Pt 7828 R 24 24 Firmware by Moxa

Pt 7828 R 24 Firmware by Moxa

Pt 7828 R 24 Hv Firmware by Moxa

Pt 7828 R 48 48 Firmware by Moxa

Pt 7828 R 48 Firmware by Moxa

Pt 7828 R 48 Hv Firmware by Moxa

Pt 7828 R Hv Firmware by Moxa

Pt 7828 R Hv Hv Firmware by Moxa