CVE-2021-22779

Q: What is the severity of CVE-2021-22779?

CVE-2021-22779 has a CVSS score of 9.1 (CRITICAL). This vulnerability allows attackers to bypass authentication and gain unauthorized read/write access to industrial controllers by spoofing Modbus communications between engineering software and controllers. It affects Schneider Electric's EcoStruxure Control Expert, Process Expert, SCADAPack RemoteConnect, and Modicon PLCs. This could lead to manipulation of industrial control systems.

9.1 CRITICAL

Authentication Bypass

📋 TL;DR

This vulnerability allows attackers to bypass authentication and gain unauthorized read/write access to industrial controllers by spoofing Modbus communications between engineering software and controllers. It affects Schneider Electric's EcoStruxure Control Expert, Process Expert, SCADAPack RemoteConnect, and Modicon PLCs. This could lead to manipulation of industrial control systems.

💻 Affected Systems

Products:

EcoStruxure Control Expert
EcoStruxure Process Expert
EcoStruxure Hybrid DCS
SCADAPack RemoteConnect for x70
Modicon M580 CPU
Modicon M340 CPU

Versions: All versions prior to EcoStruxure Control Expert V15.0 SP1, including all versions of Unity Pro; all versions of other affected products

Operating Systems: Windows (for engineering software)

Default Config Vulnerable: ⚠️ Yes

Notes: Affects both engineering station software and PLC controllers; vulnerability exists in Modbus communication protocol implementation.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete compromise of industrial control systems allowing attackers to manipulate physical processes, cause equipment damage, disrupt operations, or create safety hazards in critical infrastructure.

🟠

Likely Case

Unauthorized access to controller logic and data, enabling reconnaissance, data theft, or manipulation of industrial processes without physical access.

🟢

If Mitigated

Limited impact with proper network segmentation, monitoring, and authentication controls that detect and block unauthorized Modbus communications.

🌐 Internet-Facing: HIGH if controllers are directly exposed to internet, as exploit requires only network access to Modbus ports.

🏢 Internal Only: HIGH as internal attackers or compromised internal systems can exploit this without authentication to gain controller access.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Exploitation requires network access to Modbus ports (typically TCP 502) and ability to spoof communications; no authentication required.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: EcoStruxure Control Expert V15.0 SP1 or later

Vendor Advisory: http://download.schneider-electric.com/files?p_Doc_Ref=SEVD-2021-194-01

Restart Required: Yes

Instructions:

1. Download and install EcoStruxure Control Expert V15.0 SP1 or later from Schneider Electric. 2. Update all affected PLC firmware to latest versions. 3. Restart engineering stations and controllers after updates.

🔧 Temporary Workarounds

Network Segmentation

all

Isolate control network from corporate/IT networks using firewalls

Modbus Port Restriction

all

Block unauthorized access to Modbus TCP port 502 using firewall rules

# Windows firewall: netsh advfirewall firewall add rule name="Block Modbus" dir=in action=block protocol=TCP localport=502
# Linux iptables: iptables -A INPUT -p tcp --dport 502 -j DROP

🧯 If You Can't Patch

Implement strict network segmentation to isolate control systems from untrusted networks
Deploy intrusion detection systems monitoring for unauthorized Modbus communications and spoofing attempts

🔍 How to Verify

Check if Vulnerable:

Check if using affected software versions and if Modbus ports are accessible from untrusted networks

Check Version:

# For EcoStruxure Control Expert: Check Help > About in application

Verify Fix Applied:

Verify installation of EcoStruxure Control Expert V15.0 SP1 or later and updated PLC firmware

📡 Detection & Monitoring

Log Indicators:

Unauthorized connection attempts to Modbus ports
Unexpected engineering software connections
Multiple failed authentication attempts followed by successful access

Network Indicators:

Spoofed Modbus packets from unexpected IP addresses
Modbus traffic from non-engineering stations
Abnormal Modbus function codes or addressing

SIEM Query:

source="firewall" dest_port=502 AND (src_ip NOT IN [authorized_engineering_ips])

📊 Metadata

CVE ID: CVE-2021-22779

CVSS v3 Score: 9.1 (CRITICAL)

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

CWE: CWE-290

Published: July 14, 2021

Last Updated: November 21, 2024

🔗 References

http://download.schneider-electric.com/files?p_Doc_Ref=SEVD-2021-194-01 Vendor Advisory
http://download.schneider-electric.com/files?p_Doc_Ref=SEVD-2021-194-01 Vendor Advisory

📋 TL;DR

💻 Affected Systems

📦 What is this software?

Ecostruxure Control Expert by Schneider Electric

Ecostruxure Control Expert by Schneider Electric

Ecostruxure Control Expert by Schneider Electric

Ecostruxure Process Expert by Schneider Electric

Modicon M340 Bmxp341000 Firmware by Schneider Electric

Modicon M340 Bmxp342010 Firmware by Schneider Electric

Modicon M340 Bmxp342020 Firmware by Schneider Electric

Modicon M340 Bmxp342030 Firmware by Schneider Electric

Modicon M580 Bmeh582040 Firmware by Schneider Electric

Modicon M580 Bmeh582040c Firmware by Schneider Electric

Modicon M580 Bmeh582040s Firmware by Schneider Electric

Modicon M580 Bmeh584040 Firmware by Schneider Electric

Modicon M580 Bmeh584040c Firmware by Schneider Electric

Modicon M580 Bmeh584040s Firmware by Schneider Electric

Modicon M580 Bmeh586040 Firmware by Schneider Electric

Modicon M580 Bmeh586040c Firmware by Schneider Electric

Modicon M580 Bmeh586040s Firmware by Schneider Electric

Modicon M580 Bmep581020 Firmware by Schneider Electric

Modicon M580 Bmep581020h Firmware by Schneider Electric

Modicon M580 Bmep582020 Firmware by Schneider Electric

Modicon M580 Bmep582020h Firmware by Schneider Electric

Modicon M580 Bmep582040 Firmware by Schneider Electric

Modicon M580 Bmep582040h Firmware by Schneider Electric

Modicon M580 Bmep582040s Firmware by Schneider Electric

Modicon M580 Bmep583020 Firmware by Schneider Electric

Modicon M580 Bmep583040 Firmware by Schneider Electric

Modicon M580 Bmep584020 Firmware by Schneider Electric

Modicon M580 Bmep584040 Firmware by Schneider Electric

Modicon M580 Bmep584040s Firmware by Schneider Electric

Modicon M580 Bmep585040 Firmware by Schneider Electric

Modicon M580 Bmep585040c Firmware by Schneider Electric

Modicon M580 Bmep586040 Firmware by Schneider Electric

Modicon M580 Bmep586040c Firmware by Schneider Electric

Remoteconnect by Schneider Electric

⚠️ Risk & Real-World Impact

Worst Case

Likely Case

If Mitigated

🎯 Exploit Status

🛠️ Fix & Mitigation

✅ Official Fix

Instructions:

🔧 Temporary Workarounds

Network Segmentation

Modbus Port Restriction

🧯 If You Can't Patch

🔍 How to Verify

Check if Vulnerable:

Check Version:

Verify Fix Applied:

📡 Detection & Monitoring

Log Indicators:

Network Indicators:

SIEM Query:

📊 Metadata

🔗 References

📤 Share & Export

🔗 Related Vulnerabilities