CVE-2021-31345 – This vulnerability in Siemens industrial contro... (How to Fix)

Q: How do I fix CVE-2021-31345?

1. Check affected product versions. 2. Download and apply Siemens security updates. 3. Restart affected systems. 4. Verify patch installation.

Q: What is the severity of CVE-2021-31345?

CVE-2021-31345 has a CVSS score of 7.5 (HIGH). This vulnerability in Siemens industrial control systems allows attackers to send malformed UDP packets with unchecked payload lengths, potentially causing information leaks or denial-of-service conditions. It affects Capital Embedded AR Classic and PLUSCONTROL 1st Gen products used in industrial automation environments. The impact depends on user applications running on top of UDP.

📋 TL;DR

This vulnerability in Siemens industrial control systems allows attackers to send malformed UDP packets with unchecked payload lengths, potentially causing information leaks or denial-of-service conditions. It affects Capital Embedded AR Classic and PLUSCONTROL 1st Gen products used in industrial automation environments. The impact depends on user applications running on top of UDP.

💻 Affected Systems

Products:

Capital Embedded AR Classic 431-422
Capital Embedded AR Classic R20-11
PLUSCONTROL 1st Gen

Versions: All versions for 431-422 and PLUSCONTROL 1st Gen; R20-11 versions < V2303

Operating Systems: Embedded industrial control systems

Default Config Vulnerable: ⚠️ Yes

Notes: Vulnerability exists in UDP protocol handling; impact depends on user applications running on affected devices.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Critical industrial processes disrupted through DoS, sensitive operational data leaked, or cascading failures in industrial control systems.

🟠

Likely Case

Service disruption affecting specific industrial automation functions, potentially causing production downtime or equipment malfunctions.

🟢

If Mitigated

Minimal impact with proper network segmentation and monitoring; isolated incidents affecting non-critical systems.

🌐 Internet-Facing: MEDIUM

🏢 Internal Only: HIGH

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Exploitation requires network access to UDP services; no authentication needed to send malformed packets.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: V2303 for Capital Embedded AR Classic R20-11

Vendor Advisory: https://cert-portal.siemens.com/productcert/html/ssa-044112.html

Restart Required: Yes

Instructions:

1. Check affected product versions. 2. Download and apply Siemens security updates. 3. Restart affected systems. 4. Verify patch installation.

🔧 Temporary Workarounds

Network Segmentation

all

Isolate affected industrial control systems from untrusted networks using firewalls and VLANs.

UDP Port Filtering

all

Block unnecessary UDP traffic to affected devices at network perimeter.

🧯 If You Can't Patch

Implement strict network access controls to limit UDP traffic to trusted sources only.
Deploy intrusion detection systems to monitor for malformed UDP packets and unusual traffic patterns.

🔍 How to Verify

Check if Vulnerable:

Check product version against affected versions list; review system logs for UDP packet handling errors.

Check Version:

Product-specific commands vary; consult Siemens documentation for version checking on each affected platform.

Verify Fix Applied:

Confirm installation of V2303 or later for R20-11; verify no UDP length validation issues in testing.

📡 Detection & Monitoring

Log Indicators:

UDP packet handling errors
Buffer overflow warnings
Service disruption logs

Network Indicators:

Unusually large UDP packets
Malformed IP headers
Unexpected UDP traffic to industrial control ports

SIEM Query:

source_port:udp AND (packet_size:>threshold OR malformed_header:true) AND dest_ip:industrial_control_subnet

📊 Metadata

CVE ID: CVE-2021-31345

CVSS v3 Score: 7.5 (HIGH)

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

CWE: CWE-1284

Published: November 9, 2021

Last Updated: November 21, 2024

🔗 References

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