CVE-2020-25242 – A vulnerability in Siemens SIMATIC NET CP 343-1... (How to Fix)

Q: What is the severity of CVE-2020-25242?

CVE-2020-25242 has a CVSS score of 7.5 (HIGH). A vulnerability in Siemens SIMATIC NET CP 343-1 communication processors allows remote attackers to cause a Denial-of-Service condition by sending specially crafted packets to TCP port 102. Affected devices include all versions of CP 343-1 Advanced, Lean, and Standard variants, requiring a cold restart to recover from the attack.

📋 TL;DR

A vulnerability in Siemens SIMATIC NET CP 343-1 communication processors allows remote attackers to cause a Denial-of-Service condition by sending specially crafted packets to TCP port 102. Affected devices include all versions of CP 343-1 Advanced, Lean, and Standard variants, requiring a cold restart to recover from the attack.

💻 Affected Systems

Products:

SIMATIC NET CP 343-1 Advanced (incl. SIPLUS variants)
SIMATIC NET CP 343-1 Lean (incl. SIPLUS variants)
SIMATIC NET CP 343-1 Standard (incl. SIPLUS variants)

Versions: All versions

Operating Systems: Embedded firmware on Siemens industrial devices

Default Config Vulnerable: ⚠️ Yes

Notes: All variants including SIPLUS industrial versions are affected; TCP port 102 (ISO-TSAP) is typically open by default for PROFINET communication.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete loss of industrial control system communication, requiring physical intervention and cold restart of affected devices, potentially disrupting manufacturing or industrial processes.

🟠

Likely Case

Temporary disruption of industrial network communications until affected devices are manually restarted, causing operational downtime.

🟢

If Mitigated

Minimal impact with proper network segmentation and access controls preventing unauthorized access to port 102.

🌐 Internet-Facing: MEDIUM - While industrial devices shouldn't be internet-facing, misconfigurations could expose them; exploitation requires network access to port 102.

🏢 Internal Only: HIGH - Industrial networks often have flat architectures, allowing lateral movement; any internal attacker with network access could exploit this.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Exploitation requires sending specially crafted packets to TCP port 102; no authentication required; specific packet structure not publicly documented.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Contact Siemens for specific firmware updates

Vendor Advisory: https://cert-portal.siemens.com/productcert/pdf/ssa-676775.pdf

Restart Required: Yes

Instructions:

1. Contact Siemens support for firmware updates
2. Schedule maintenance window for industrial systems
3. Backup device configurations
4. Apply firmware update following Siemens documentation
5. Perform cold restart of affected devices
6. Verify communication restoration

🔧 Temporary Workarounds

Network Segmentation

all

Restrict access to TCP port 102 using firewall rules and network segmentation

# Example firewall rule to block external access to port 102
iptables -A INPUT -p tcp --dport 102 -j DROP
# Allow only from trusted PROFINET controllers
iptables -A INPUT -p tcp --dport 102 -s [trusted_ip] -j ACCEPT

Access Control Lists

all

Implement strict network access controls to limit which devices can communicate with affected CP 343-1 processors

# Example: Configure industrial switch ACLs
access-list 101 permit tcp host [controller_ip] host [cp343_ip] eq 102
access-list 101 deny tcp any host [cp343_ip] eq 102

🧯 If You Can't Patch

Implement strict network segmentation to isolate affected devices from untrusted networks
Deploy intrusion detection systems monitoring for anomalous traffic on port 102

🔍 How to Verify

Check if Vulnerable:

Check device model and firmware version against Siemens advisory; devices with model numbers 6GK7343-1EX30-0XE0, 6GK7343-1EX20-0XE0, 6GK7343-1GX20-0XE0 and variants are affected

Check Version:

Use Siemens TIA Portal or STEP 7 software to read device firmware version via PROFINET connection

Verify Fix Applied:

Verify firmware version has been updated to Siemens-provided patched version; test by attempting normal PROFINET communication

📡 Detection & Monitoring

Log Indicators:

Unusual traffic patterns on TCP port 102
Device communication failures in industrial control system logs
Multiple connection attempts to port 102 from unauthorized sources

Network Indicators:

Abnormal packet sizes or patterns on TCP port 102
Traffic to port 102 from non-PROFINET controllers
Sudden cessation of normal PROFINET communication

SIEM Query:

source_port=102 AND (packet_size>normal_range OR protocol_anomaly=true) OR dest_port=102 AND (src_ip NOT IN allowed_profinet_controllers)

📊 Metadata

CVE ID: CVE-2020-25242

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-400

Published: May 12, 2021

Last Updated: November 21, 2024

🔗 References

https://cert-portal.siemens.com/productcert/pdf/ssa-676775.pdf Vendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-676775.pdf Vendor Advisory
https://us-cert.cisa.gov/ics/advisories/icsa-21-131-07 Third Party Advisory,US Government Resource
https://cert-portal.siemens.com/productcert/pdf/ssa-676775.pdf Vendor Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-676775.pdf Vendor Advisory
https://us-cert.cisa.gov/ics/advisories/icsa-21-131-07 Third Party Advisory,US Government Resource

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