CVE-2017-7575 – This vulnerability in Schneider Electric Modico... (How to Fix)

Q: What is the severity of CVE-2017-7575?

CVE-2017-7575 has a CVSS score of 9.8 (CRITICAL). This vulnerability in Schneider Electric Modicon TM221CE16R PLCs allows remote attackers to retrieve the application-protection password via a crafted Modbus request. With this password, attackers can download, modify, and upload the PLC application program, potentially altering industrial processes. Organizations using affected Schneider Electric PLCs in industrial control systems are at risk.

📋 TL;DR

This vulnerability in Schneider Electric Modicon TM221CE16R PLCs allows remote attackers to retrieve the application-protection password via a crafted Modbus request. With this password, attackers can download, modify, and upload the PLC application program, potentially altering industrial processes. Organizations using affected Schneider Electric PLCs in industrial control systems are at risk.

💻 Affected Systems

Products:

Schneider Electric Modicon TM221CE16R

Versions: Version 1.3.3.3

Operating Systems: Embedded PLC firmware

Default Config Vulnerable: ⚠️ Yes

Notes: Affects devices with Modbus port (502/tcp) accessible. Industrial control systems using these PLCs are vulnerable.

📦 What is this software?

Modicon Tm221ce16r Firmware by Schneider Electric

View all CVEs affecting Modicon Tm221ce16r Firmware →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete compromise of industrial processes leading to physical damage, production shutdowns, or safety incidents through unauthorized program modifications.

🟠

Likely Case

Unauthorized access to PLC logic, potential program theft or tampering, and disruption of industrial operations.

🟢

If Mitigated

Limited impact with proper network segmentation and access controls preventing external access to Modbus port.

🌐 Internet-Facing: HIGH - Direct exposure of Modbus port (502/tcp) to internet allows remote exploitation without authentication.

🏢 Internal Only: MEDIUM - Internal attackers or malware could exploit if Modbus access is permitted within network.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: CONFIRMED

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Simple crafted Modbus request triggers password disclosure. Exploit code is publicly available in security advisories.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Update to firmware version beyond 1.3.3.3 (consult Schneider Electric for specific patched version)

Vendor Advisory: http://download.schneider-electric.com/files?p_Doc_Ref=SEVD-2017-097-02

Restart Required: Yes

Instructions:

1. Download updated firmware from Schneider Electric. 2. Backup current PLC program. 3. Apply firmware update via programming software. 4. Restart PLC. 5. Verify firmware version.

🔧 Temporary Workarounds

Network Segmentation

all

Isolate PLCs from untrusted networks using firewalls to block external access to Modbus port 502/tcp.

Access Control Lists

all

Implement network ACLs to restrict Modbus access only to authorized engineering stations and SCADA systems.

🧯 If You Can't Patch

Implement strict network segmentation to isolate PLCs in dedicated control network zones
Deploy industrial firewalls with deep packet inspection to detect and block malicious Modbus traffic

🔍 How to Verify

Check if Vulnerable:

Send crafted Modbus request \x00\x01\x00\x00\x00\x05\x01\x5a\x00\x03\x00 to port 502/tcp and check if password is returned in response.

Check Version:

Check PLC firmware version via Schneider Electric programming software (SoMachine, EcoStruxure Machine Expert)

Verify Fix Applied:

After patching, attempt the same exploit request; it should no longer return the application-protection password.

📡 Detection & Monitoring

Log Indicators:

Unusual Modbus traffic patterns
Multiple failed authentication attempts followed by successful access
PLC program download/uploads outside maintenance windows

Network Indicators:

Modbus requests containing \x00\x01\x00\x00\x00\x05\x01\x5a\x00\x03\x00 pattern
Unexpected connections to port 502/tcp from unauthorized sources

SIEM Query:

source_port=502 AND (payload_contains="\x00\x01\x00\x00\x00\x05\x01\x5a\x00\x03\x00" OR dest_ip=[PLC_IP])

📊 Metadata

CVE ID: CVE-2017-7575

CVSS v3 Score: 9.8 (CRITICAL)

CVSS Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-200

Published: April 6, 2017

Last Updated: April 20, 2025

🔗 References

http://download.schneider-electric.com/files?p_Doc_Ref=SEVD-2017-097-02
http://www.securityfocus.com/bid/97523 Third Party Advisory,VDB Entry
https://os-s.net/advisories/OSS-2017-01.pdf Exploit,Third Party Advisory
http://download.schneider-electric.com/files?p_Doc_Ref=SEVD-2017-097-02
http://www.securityfocus.com/bid/97523 Third Party Advisory,VDB Entry
https://os-s.net/advisories/OSS-2017-01.pdf Exploit,Third Party Advisory

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