CVE-2024-31504
📋 TL;DR
A buffer overflow vulnerability in SILA Embedded Solutions GmbH's freemodbus library (v.2018-09-12) allows remote attackers to cause denial of service via the LINUXTCP server component. This affects systems using this specific version of freemodbus with the LINUXTCP server enabled. The vulnerability stems from improper bounds checking in buffer operations.
💻 Affected Systems
- SILA Embedded Solutions GmbH freemodbus
📦 What is this software?
Freemodbus by Embedded Solutions
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise if the buffer overflow can be leveraged for arbitrary code execution, though CWE-120 typically results in crashes.
Likely Case
Denial of service causing the freemodbus service to crash, disrupting Modbus TCP communications and potentially affecting industrial control systems.
If Mitigated
Minimal impact if the service is isolated, monitored, and crashes are automatically recovered without affecting critical operations.
🎯 Exploit Status
The provided references include proof-of-concept details, making exploitation straightforward for attackers with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified
Vendor Advisory: Not available
Restart Required: No
Instructions:
No official patch is available. Consider upgrading to a newer version of freemodbus if one exists, or apply workarounds.
🔧 Temporary Workarounds
Disable LINUXTCP Server
linuxIf the LINUXTCP server is not required, disable it to remove the attack surface.
Modify configuration to disable TCP server or stop the service.
Network Segmentation
linuxRestrict network access to the freemodbus service using firewalls.
iptables -A INPUT -p tcp --dport 502 -j DROP
ufw deny 502/tcp
🧯 If You Can't Patch
- Implement strict network access controls to limit exposure to trusted sources only.
- Monitor system logs for crash events and set up automated alerts for service failures.
🔍 How to Verify
Check if Vulnerable:
Check if freemodbus version 2018-09-12 is installed and the LINUXTCP server is running on port 502 (default Modbus TCP port).Check Version:
Check application logs or configuration files for version information; no standard command is provided by the vendor.Verify Fix Applied:
Verify that the LINUXTCP server is disabled or network access is restricted, and test that the service no longer crashes under attack conditions.📡 Detection & Monitoring
Log Indicators:
- Unexpected crashes or restarts of the freemodbus service
- Error messages related to buffer overflows or segmentation faults
Network Indicators:
- Unusual traffic patterns to port 502 (Modbus TCP)
- Connection attempts from untrusted sources
SIEM Query:
source="freemodbus.log" AND ("crash" OR "segmentation fault" OR "buffer overflow")