CVE-2021-31571
📋 TL;DR
CVE-2021-31571 is an integer overflow vulnerability in Amazon Web Services FreeRTOS kernel's queue creation function. This allows attackers to cause heap corruption, potentially leading to remote code execution or denial of service. Systems running AWS FreeRTOS versions before 10.4.3 are affected.
💻 Affected Systems
- Amazon Web Services FreeRTOS
📦 What is this software?
Freertos by Amazon
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with kernel privileges leading to complete system compromise
Likely Case
Denial of service through system crash or instability
If Mitigated
Limited impact with proper memory protection and isolation mechanisms
🎯 Exploit Status
Exploitation requires triggering queue creation with malicious parameters
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 10.4.3 and later
Vendor Advisory: https://github.com/FreeRTOS/FreeRTOS-Kernel/commit/47338393f1f79558f6144213409f09f81d7c4837
Restart Required: Yes
Instructions:
1. Update FreeRTOS kernel to version 10.4.3 or later
2. Recompile your embedded application
3. Flash updated firmware to affected devices
4. Verify functionality after update
🔧 Temporary Workarounds
Input validation for queue parameters
allAdd bounds checking for queue size parameters before calling queue creation functions
// Add validation in application code:
if (uxQueueLength > MAX_SAFE_QUEUE_SIZE || uxItemSize > MAX_SAFE_ITEM_SIZE) {
// Handle error or use safe defaults
}
🧯 If You Can't Patch
- Implement network segmentation to isolate vulnerable IoT devices
- Deploy intrusion detection systems monitoring for abnormal queue creation patterns
🔍 How to Verify
Check if Vulnerable:
Check FreeRTOS kernel version in source code or firmware metadataCheck Version:
grep -r "tskKERNEL_VERSION_NUMBER" in source code or check firmware version stringsVerify Fix Applied:
Verify kernel version is 10.4.3+ and check for commit 47338393f1f79558f6144213409f09f81d7c4837📡 Detection & Monitoring
Log Indicators:
- Multiple failed queue creation attempts
- System crashes or reboots after queue operations
- Memory allocation errors in kernel logs
Network Indicators:
- Unusual network traffic to/from IoT devices
- Protocol anomalies in device communications
SIEM Query:
source="device_logs" AND ("queue creation failed" OR "kernel panic" OR "memory corruption")