CVE-2024-1638
📋 TL;DR
This vulnerability in Zephyr RTOS Bluetooth stack allows unauthorized read/write access to Bluetooth characteristics that should require LE Secure Connections encryption. Attackers can bypass security controls to access sensitive data or modify device behavior. This affects any Zephyr-based IoT/embedded devices using Bluetooth LE with specific permission configurations.
💻 Affected Systems
- Zephyr RTOS
📦 What is this software?
Zephyr by Zephyrproject
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of Bluetooth-enabled device allowing data exfiltration, unauthorized control, or injection of malicious firmware updates.
Likely Case
Unauthorized access to sensitive device data or configuration settings that should be protected by encryption.
If Mitigated
Minimal impact if devices use proper permission combinations or don't rely solely on BT_GATT_PERM_READ_LESC/BT_GATT_PERM_WRITE_LESC permissions.
🎯 Exploit Status
Exploitation requires Bluetooth proximity and knowledge of vulnerable characteristic UUIDs. No authentication needed when permissions are misconfigured.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Zephyr v3.6.0 and later
Vendor Advisory: https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-p6f3-f63q-5mc2
Restart Required: Yes
Instructions:
1. Update Zephyr RTOS to version 3.6.0 or later. 2. Rebuild and flash firmware to affected devices. 3. Verify permission combinations in Bluetooth GATT characteristics.
🔧 Temporary Workarounds
Modify Bluetooth Permission Combinations
allEnsure BT_GATT_PERM_READ_LESC and BT_GATT_PERM_WRITE_LESC are always combined with appropriate encryption/authentication permissions in source code.
// In Bluetooth characteristic definitions:
// Replace: .perm = BT_GATT_PERM_READ_LESC
// With: .perm = BT_GATT_PERM_READ_LESC | BT_GATT_PERM_READ_ENCRYPT
🧯 If You Can't Patch
- Disable Bluetooth functionality on affected devices if not required
- Implement network segmentation to isolate Bluetooth-enabled devices from critical networks
🔍 How to Verify
Check if Vulnerable:
Review Bluetooth GATT characteristic definitions in source code for BT_GATT_PERM_READ_LESC or BT_GATT_PERM_WRITE_LESC used without combined encryption/authentication permissions.Check Version:
Check Zephyr version in project configuration or build outputVerify Fix Applied:
Check that Zephyr version is 3.6.0+ and verify permission combinations in Bluetooth characteristic definitions include proper encryption flags.📡 Detection & Monitoring
Log Indicators:
- Unexpected Bluetooth characteristic access attempts
- Unauthorized GATT read/write operations
Network Indicators:
- Bluetooth traffic to characteristics that should be encrypted
- Unencrypted LE Secure Connections traffic
SIEM Query:
Not applicable for embedded Bluetooth traffic detection