CVE-2018-5440
📋 TL;DR
A stack-based buffer overflow vulnerability in CODESYS Web Server allows remote attackers to execute arbitrary code or cause denial-of-service by sending crafted requests. Affects CODESYS web servers running stand-alone Version 2.3 or as part of CODESYS runtime systems prior to V1.1.9.19 on Windows and Windows CE platforms.
💻 Affected Systems
- 3S-Smart CODESYS Web Server
- CODESYS runtime system with web server component
📦 What is this software?
Codesys Web Server by 3s Software
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with SYSTEM/administrator privileges leading to complete system compromise, lateral movement, and persistent backdoor installation.
Likely Case
Denial-of-service causing web server crashes and disruption of industrial control operations, with potential for limited code execution.
If Mitigated
Isolated denial-of-service with no code execution due to network segmentation and exploit mitigations.
🎯 Exploit Status
Exploitation requires sending crafted HTTP requests to the web server. No authentication is required, making this easily exploitable.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: V1.1.9.19 or later for runtime systems, updated stand-alone version
Vendor Advisory: https://ics-cert.us-cert.gov/advisories/ICSA-18-032-02
Restart Required: Yes
Instructions:
1. Download updated CODESYS runtime system V1.1.9.19 or later from 3S-Smart. 2. Stop the CODESYS web server service. 3. Install the update. 4. Restart the service. 5. Verify the version is updated.
🔧 Temporary Workarounds
Network Segmentation
allIsolate CODESYS web servers from untrusted networks using firewalls or network segmentation.
Disable Web Server
windowsDisable the CODESYS web server if not required for operations.
sc stop "CODESYS Web Server"
sc config "CODESYS Web Server" start= disabled
🧯 If You Can't Patch
- Implement strict network access controls to limit access to CODESYS web servers only from trusted IP addresses.
- Deploy intrusion detection/prevention systems to monitor for buffer overflow exploitation attempts against the web server.
🔍 How to Verify
Check if Vulnerable:
Check CODESYS runtime system version: if prior to V1.1.9.19 or using stand-alone web server Version 2.3, the system is vulnerable.Check Version:
Check CODESYS control panel or runtime configuration for version information.Verify Fix Applied:
Verify CODESYS runtime system version is V1.1.9.19 or later, and web server is no longer Version 2.3.📡 Detection & Monitoring
Log Indicators:
- Web server crash logs
- Unusual HTTP requests with long parameters or malformed headers
- Access attempts from unexpected IP addresses
Network Indicators:
- HTTP requests with unusually long content-length or parameters
- Multiple connection attempts to CODESYS web server port (default 80/8080)
- Traffic patterns indicating buffer overflow exploitation
SIEM Query:
source="CODESYS" AND (event="crash" OR http_request_length>10000)