CVE-2021-3323
📋 TL;DR
This CVE describes an integer underflow vulnerability in the 6LoWPAN IPHC header uncompression functionality in Zephyr RTOS. An attacker could exploit this to cause memory corruption, potentially leading to denial of service or arbitrary code execution. This affects Zephyr-based IoT devices using 6LoWPAN networking.
💻 Affected Systems
- Zephyr RTOS
📦 What is this software?
Zephyr by Zephyrproject
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, data exfiltration, or device becoming part of botnet
Likely Case
Denial of service through device crash or reboot, potentially disrupting IoT network operations
If Mitigated
Limited impact if proper network segmentation and input validation are in place
🎯 Exploit Status
Exploitation requires sending specially crafted 6LoWPAN packets to vulnerable devices
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in Zephyr 2.5.0 and later
Vendor Advisory: https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-89j6-qpxf-pfpc
Restart Required: Yes
Instructions:
1. Update Zephyr RTOS to version 2.5.0 or later
2. Rebuild and redeploy firmware to affected devices
3. Verify the fix by testing 6LoWPAN functionality
🔧 Temporary Workarounds
Disable 6LoWPAN IPHC compression
allDisable IPHC header compression in 6LoWPAN configuration to prevent exploitation
CONFIG_NET_6LO_IPHC=n
Network segmentation
allIsolate 6LoWPAN networks from untrusted networks using firewalls or VLANs
🧯 If You Can't Patch
- Implement strict network access controls to limit 6LoWPAN traffic to trusted sources only
- Deploy network intrusion detection systems to monitor for anomalous 6LoWPAN traffic patterns
🔍 How to Verify
Check if Vulnerable:
Check Zephyr version and 6LoWPAN configuration: if version >=2.4.0 and CONFIG_NET_6LO_IPHC=y, device is vulnerableCheck Version:
Check Zephyr version in build configuration or device firmware informationVerify Fix Applied:
Verify Zephyr version is >=2.5.0 and test 6LoWPAN functionality with malformed packets📡 Detection & Monitoring
Log Indicators:
- Device crashes or reboots
- 6LoWPAN stack errors
- Memory corruption warnings
Network Indicators:
- Malformed 6LoWPAN packets
- Unusual traffic patterns to IoT devices
- Protocol violations in 6LoWPAN headers
SIEM Query:
Search for: device_type:"zephyr" AND (event:"crash" OR event:"reboot") AND protocol:"6lowpan"