CVE-2024-40493
📋 TL;DR
A null pointer dereference vulnerability in FreeCoAP 1.0 allows remote attackers to cause denial of service or potentially execute arbitrary code by sending specially crafted CoAP packets. This affects all systems using the vulnerable FreeCoAP library for CoAP protocol communication.
💻 Affected Systems
- Keith Cullen FreeCoAP
📦 What is this software?
Freecoap by Keith Cullen
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or persistent backdoor installation
Likely Case
Denial of service causing application crashes and service disruption
If Mitigated
Limited impact with proper network segmentation and exploit prevention controls
🎯 Exploit Status
Proof of concept available in GitHub issue; exploitation requires sending crafted CoAP packets
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check GitHub issue #37 for fix status
Vendor Advisory: https://github.com/keith-cullen/FreeCoAP/issues/37
Restart Required: Yes
Instructions:
1. Monitor GitHub issue #37 for official patch 2. Apply patch when available 3. Recompile FreeCoAP 4. Restart affected services
🔧 Temporary Workarounds
Network filtering
linuxBlock or filter CoAP traffic at network boundaries
iptables -A INPUT -p udp --dport 5683 -j DROP
iptables -A INPUT -p udp --dport 5684 -j DROP
Service isolation
allRun FreeCoAP services in isolated network segments
🧯 If You Can't Patch
- Implement strict network segmentation to isolate FreeCoAP services
- Deploy intrusion prevention systems to detect and block CoAP exploit attempts
🔍 How to Verify
Check if Vulnerable:
Check if FreeCoAP 1.0 is installed and if coap_client_exchange_blockwise2 function is usedCheck Version:
Check build configuration or source code for FreeCoAP versionVerify Fix Applied:
Verify patch applied by checking version or testing with crafted CoAP packets📡 Detection & Monitoring
Log Indicators:
- Application crashes
- Memory access violation errors
- Unexpected process termination
Network Indicators:
- Malformed CoAP packets
- Unusual CoAP traffic patterns
- Exploit attempt signatures
SIEM Query:
source="*coap*" AND (event_type="crash" OR error="segmentation fault" OR error="null pointer")