CVE-2021-32968 – Two buffer overflow vulnerabilities in the buil... (How to Fix)

Q: What is the severity of CVE-2021-32968?

CVE-2021-32968 has a CVSS score of 7.5 (HIGH). Two buffer overflow vulnerabilities in the built-in web server of Moxa NPort IAW5000A-I/O Series devices allow remote attackers to cause denial-of-service conditions. These affect firmware version 2.2 and earlier, potentially disrupting industrial serial device server operations.

📋 TL;DR

Two buffer overflow vulnerabilities in the built-in web server of Moxa NPort IAW5000A-I/O Series devices allow remote attackers to cause denial-of-service conditions. These affect firmware version 2.2 and earlier, potentially disrupting industrial serial device server operations.

💻 Affected Systems

Products:

Moxa NPort IAW5000A-I/O Series

Versions: Firmware version 2.2 and earlier

Operating Systems: Embedded firmware

Default Config Vulnerable: ⚠️ Yes

Notes: All devices with web server enabled are vulnerable by default

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution leading to complete device compromise and potential lateral movement into industrial control networks

🟠

Likely Case

Denial-of-service causing device reboot or unresponsiveness, disrupting serial communications

🟢

If Mitigated

Limited impact with proper network segmentation and access controls

🌐 Internet-Facing: HIGH - Directly exposed devices can be exploited remotely without authentication

🏢 Internal Only: MEDIUM - Requires internal network access but still exploitable without credentials

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Buffer overflows in web server suggest relatively straightforward exploitation

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Firmware version 2.3 or later

Vendor Advisory: https://www.moxa.com/en/support/product-support/security-advisory/nport-iaw5000a-io-serial-device-server-vulnerabilities

Restart Required: Yes

Instructions:

1. Download firmware version 2.3 or later from Moxa website
2. Backup current configuration
3. Upload new firmware via web interface or console
4. Reboot device
5. Restore configuration if needed

🔧 Temporary Workarounds

Disable web server

all

Disable the built-in web server if not required for operations

Network segmentation

all

Isolate devices in separate VLAN with strict firewall rules

🧯 If You Can't Patch

Implement strict network access controls to limit device exposure
Monitor for abnormal traffic patterns and device reboots

🔍 How to Verify

Check if Vulnerable:

Check firmware version via web interface at http://device-ip/ or via serial console

Check Version:

curl -s http://device-ip/ | grep -i firmware

Verify Fix Applied:

Verify firmware version is 2.3 or later and test web server functionality

📡 Detection & Monitoring

Log Indicators:

Multiple connection attempts to web server
Device reboot events
Web server crash logs

Network Indicators:

Unusual HTTP requests to device web interface
Traffic patterns suggesting buffer overflow attempts

SIEM Query:

source="device_logs" AND (event="reboot" OR event="crash") AND device_type="Moxa NPort IAW5000A"

📊 Metadata

CVE ID: CVE-2021-32968

CVSS v3 Score: 7.5 (HIGH)

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

CWE: CWE-120

Published: April 1, 2022

Last Updated: November 21, 2024

🔗 References

https://www.cisa.gov/uscert/ics/advisories/icsa-21-187-01 Mitigation,Third Party Advisory,US Government Resource
https://www.moxa.com/en/support/product-support/security-advisory/nport-iaw5000a-io-serial-device-server-vulnerabilities Third Party Advisory
https://www.cisa.gov/uscert/ics/advisories/icsa-21-187-01 Mitigation,Third Party Advisory,US Government Resource
https://www.moxa.com/en/support/product-support/security-advisory/nport-iaw5000a-io-serial-device-server-vulnerabilities Third Party Advisory

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