CVE-2021-20986

Q: What is the severity of CVE-2021-20986?

CVE-2021-20986 has a CVSS score of 7.5 (HIGH). A Denial of Service vulnerability in Hilscher PROFINET IO Device V3 allows attackers to disrupt industrial communication by causing unexpected loss of cyclic communication or interruption of acyclic communication. This affects industrial control systems using Hilscher PROFINET IO Device V3 versions prior to V3.14.0.7 in manufacturing, energy, and critical infrastructure environments.

7.5 HIGH

Denial of Service

📋 TL;DR

A Denial of Service vulnerability in Hilscher PROFINET IO Device V3 allows attackers to disrupt industrial communication by causing unexpected loss of cyclic communication or interruption of acyclic communication. This affects industrial control systems using Hilscher PROFINET IO Device V3 versions prior to V3.14.0.7 in manufacturing, energy, and critical infrastructure environments.

💻 Affected Systems

Products:

Hilscher PROFINET IO Device V3

Versions: All versions prior to V3.14.0.7

Operating Systems: Embedded firmware

Default Config Vulnerable: ⚠️ Yes

Notes: Affects devices in PROFINET industrial networks; vulnerability is protocol-specific and requires PROFINET communication access.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete disruption of PROFINET communication leading to production stoppage, equipment damage, or safety system failures in industrial environments.

🟠

Likely Case

Temporary loss of communication between controllers and field devices causing production delays and requiring manual intervention to restore operations.

🟢

If Mitigated

Minimal impact with proper network segmentation and monitoring allowing quick detection and recovery from communication interruptions.

🌐 Internet-Facing: LOW with brief explanation

🏢 Internal Only: HIGH with brief explanation

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Exploitation requires network access to PROFINET communication but no authentication; likely simple packet manipulation.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: V3.14.0.7

Vendor Advisory: https://kb.hilscher.com/display/ISMS/2020-12-03+Denial+of+Service+vulnerability+in+PROFINET+IO+Device

Restart Required: Yes

Instructions:

1. Download firmware V3.14.0.7 from Hilscher support portal. 2. Backup current configuration. 3. Upload new firmware via device management interface. 4. Restart device. 5. Verify firmware version and restore configuration if needed.

🔧 Temporary Workarounds

Network Segmentation

all

Isolate PROFINET networks from other networks using firewalls or VLANs to limit attack surface.

Access Control Lists

all

Implement strict network ACLs to allow only authorized PROFINET traffic to affected devices.

🧯 If You Can't Patch

Implement strict network segmentation to isolate PROFINET devices from untrusted networks
Deploy network monitoring and intrusion detection specifically for PROFINET traffic anomalies

🔍 How to Verify

Check if Vulnerable:

Check device firmware version via device web interface or management software; versions below V3.14.0.7 are vulnerable.

Check Version:

Use Hilscher netX Studio or device web interface to check firmware version

Verify Fix Applied:

Confirm firmware version shows V3.14.0.7 or higher in device management interface and verify normal PROFINET communication.

📡 Detection & Monitoring

Log Indicators:

Unexpected PROFINET communication drops
Device restart logs
Cyclic communication failure alerts

Network Indicators:

Abnormal PROFINET packet patterns
Sudden increase in PROFINET error frames
Communication timeouts between controllers and devices

SIEM Query:

source="PROFINET" AND (event_type="communication_failure" OR event_type="device_restart")

📊 Metadata

CVE ID: CVE-2021-20986

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-787

Published: February 16, 2021

Last Updated: November 21, 2024

🔗 References

https://cert.vde.com/en-us/advisories/vde-2021-006 Third Party Advisory
https://kb.hilscher.com/display/ISMS/2020-12-03+Denial+of+Service+vulnerability+in+PROFINET+IO+Device Vendor Advisory
https://cert.vde.com/en-us/advisories/vde-2021-006 Third Party Advisory
https://kb.hilscher.com/display/ISMS/2020-12-03+Denial+of+Service+vulnerability+in+PROFINET+IO+Device Vendor Advisory

📋 TL;DR

💻 Affected Systems

📦 What is this software?

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