CVE-2021-22787
📋 TL;DR
This vulnerability allows remote attackers to cause denial of service on Schneider Electric Modicon industrial control devices by sending specially crafted HTTP requests to the web server. Affected products include Modicon M340 CPUs, M340 Ethernet modules, Premium processors, Quantum processors, and various communication modules. The vulnerability stems from improper input validation in the web server component.
💻 Affected Systems
- Modicon M340 CPUs: BMXP34
- Modicon M340 X80 Ethernet Communication Modules: BMXNOE0100 (H), BMXNOE0110 (H), BMXNOC0401, BMXNOR0200H RTU
- Modicon Premium Processors with integrated Ethernet (Copro): TSXP574634, TSXP575634, TSXP576634
- Modicon Quantum Processors with Integrated Ethernet (Copro): 140CPU65xxxxx
- Modicon Quantum Communication Modules: 140NOE771x1, 140NOC78x00, 140NOC77101
- Modicon Premium Communication Modules: TSXETY4103, TSXETY5103
📦 What is this software?
140cpu65150 Firmware by Schneider Electric
140noc77101 Firmware by Schneider Electric
140noc78x00 Firmware by Schneider Electric
140noe771x1 Firmware by Schneider Electric
Bmxnoc0401 Firmware by Schneider Electric
Bmxnoe0100 Firmware by Schneider Electric
Bmxnoe0110 Firmware by Schneider Electric
Bmxnor0200h Rtu Firmware by Schneider Electric
Modicon M340 Bmxp342020 Firmware by Schneider Electric
Tsxety4103 Firmware by Schneider Electric
Tsxety5103 Firmware by Schneider Electric
Tsxp574634 Firmware by Schneider Electric
Tsxp575634 Firmware by Schneider Electric
Tsxp576634 Firmware by Schneider Electric
⚠️ Risk & Real-World Impact
Worst Case
Complete device unavailability requiring physical reset or replacement, potentially disrupting industrial processes and causing production downtime.
Likely Case
Temporary denial of service requiring device reboot, causing operational disruption until service is restored.
If Mitigated
No impact if devices are properly segmented and not exposed to untrusted networks.
🎯 Exploit Status
Exploitation requires sending a specially crafted HTTP request to the device's web server. No authentication is required, making this easily exploitable by anyone with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: BMXP34: V3.40; Other products: No firmware patch available, mitigation through network segmentation recommended
Vendor Advisory: https://download.schneider-electric.com/files?p_Doc_Ref=SEVD-2021-257-02
Restart Required: Yes
Instructions:
1. Download firmware update from Schneider Electric website. 2. Backup device configuration. 3. Apply firmware update following vendor instructions. 4. Restart device. 5. Verify firmware version and functionality.
🔧 Temporary Workarounds
Network Segmentation
allIsolate affected devices in dedicated industrial control system networks with strict firewall rules.
Disable Web Server
allDisable the web server functionality if not required for operations.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate devices from untrusted networks
- Deploy intrusion detection systems to monitor for exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check device firmware version against affected versions list. If web server is accessible and device matches affected products/versions, it is vulnerable.Check Version:
Check firmware version through device web interface or engineering software (Unity Pro, Control Expert)Verify Fix Applied:
For BMXP34: Verify firmware version is V3.40 or later. For other devices: Verify network segmentation prevents external access to web server.📡 Detection & Monitoring
Log Indicators:
- Web server crash logs
- Device reboot events
- Unusual HTTP request patterns to device web server
Network Indicators:
- HTTP requests with malformed headers or unusual patterns to port 80/8080 on industrial devices
- Sudden loss of communication with affected devices
SIEM Query:
source="industrial-firewall" dest_port=80 OR dest_port=8080 AND (http_user_agent="malformed" OR http_request_length>threshold)