CVE-2020-7593
📋 TL;DR
A buffer overflow vulnerability in the web server of Siemens LOGO! 8 BM programmable logic controllers allows remote unauthenticated attackers to execute arbitrary code via specially crafted HTTP requests. This affects LOGO! 8 BM devices (including SIPLUS variants) running vulnerable firmware versions. Successful exploitation could give attackers full control over affected industrial control systems.
💻 Affected Systems
- Siemens LOGO! 8 BM
- Siemens SIPLUS LOGO! 8 BM
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, manipulation of industrial processes, lateral movement into OT networks, and potential physical damage or safety incidents.
Likely Case
Device crash/reboot causing process disruption, followed by persistent backdoor installation for future attacks or data exfiltration.
If Mitigated
Denial of service from malformed requests if exploit fails, but no code execution due to network segmentation and security controls.
🎯 Exploit Status
Talos Intelligence published detailed analysis and proof-of-concept. Exploitation requires sending crafted HTTP request to web server port (typically 80/tcp).
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: V1.82.03 and later
Vendor Advisory: https://cert-portal.siemens.com/productcert/pdf/ssa-573753.pdf
Restart Required: Yes
Instructions:
1. Download firmware V1.82.03 or later from Siemens Industry Online Support. 2. Use LOGO! Soft Comfort software to update device firmware. 3. Restart device after update. 4. Verify firmware version in device web interface.
🔧 Temporary Workarounds
Disable Web Server
allDisable the web server functionality if not required for operations
Configure via LOGO! Soft Comfort: Device > Parameter > Web Server > Disable
Network Segmentation
linuxIsolate LOGO! devices in separate VLAN with strict firewall rules
# Example firewall rule (adjust for your environment)
# Block external access to LOGO! web interface
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation - place LOGO! devices in isolated OT network with no internet access
- Deploy intrusion detection systems (IDS) monitoring for buffer overflow patterns in HTTP traffic to LOGO! devices
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface (http://device-ip) or LOGO! Soft Comfort software. Vulnerable if version is V1.81.01-V1.81.03, V1.82.01, or V1.82.02.Check Version:
curl -s http://device-ip/ | grep -i 'firmware\|version' or check via LOGO! Soft Comfort device propertiesVerify Fix Applied:
Confirm firmware version is V1.82.03 or later in device web interface or configuration software.📡 Detection & Monitoring
Log Indicators:
- Web server crash/restart logs
- Unusual HTTP requests with long parameters or malformed headers
- Multiple failed connection attempts to port 80
Network Indicators:
- HTTP requests with unusually long headers or parameters to LOGO! devices
- Traffic patterns matching Talos PoC signatures
- Unexpected outbound connections from LOGO! devices
SIEM Query:
source="firewall" dest_port=80 AND (http_user_agent CONTAINS "malicious" OR http_uri LENGTH > 1000) AND dest_ip IN [LOGO!_device_ips]