CVE-2021-43619
📋 TL;DR
CVE-2021-43619 is a buffer overflow vulnerability in Trusted Firmware M's Firmware Update partition that allows attackers to overwrite stack memory. This affects systems using Trusted Firmware M 1.4.x through 1.4.1 in the IPC model, potentially enabling arbitrary code execution or system compromise.
💻 Affected Systems
- Trusted Firmware M
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise through arbitrary code execution in the secure processing environment, potentially bypassing security boundaries and gaining privileged access.
Likely Case
Denial of service or limited memory corruption leading to system instability, though exploitation requires specific conditions and access.
If Mitigated
Minimal impact if proper access controls and isolation mechanisms are enforced between SPE and NSPE domains.
🎯 Exploit Status
Exploitation requires access to the firmware update interface and knowledge of memory layout. The vulnerability is in the trusted firmware layer, making detection and exploitation more complex than application-level issues.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Trusted Firmware M 1.4.2 and later
Vendor Advisory: https://developer.arm.com/support/arm-security-updates
Restart Required: Yes
Instructions:
1. Download Trusted Firmware M version 1.4.2 or later from the official repository. 2. Rebuild your firmware image with the updated Trusted Firmware M. 3. Deploy the updated firmware to affected devices. 4. Verify the update was successful and test functionality.
🔧 Temporary Workarounds
Disable Firmware Update Partition
allTemporarily disable the firmware update functionality if not required, reducing the attack surface.
# Configuration depends on specific platform - consult device documentation
Strengthen Access Controls
allImplement strict access controls to limit which processes can call psa_fwu_write functions.
# Platform-specific configuration required
🧯 If You Can't Patch
- Implement network segmentation to isolate devices with vulnerable firmware from critical systems
- Monitor for unusual firmware update attempts or memory access patterns in system logs
🔍 How to Verify
Check if Vulnerable:
Check the Trusted Firmware M version in your firmware build configuration or device documentation. If using version 1.4.0, 1.4.1, or any 1.4.x before 1.4.2, you are vulnerable.Check Version:
# Check your firmware build configuration for TF-M_VERSION variable or consult device documentationVerify Fix Applied:
Verify that Trusted Firmware M version is 1.4.2 or later in your firmware build. Test firmware update functionality to ensure it works without triggering buffer overflow conditions.📡 Detection & Monitoring
Log Indicators:
- Unusual firmware write operations
- Memory access violations in secure processing environment
- System crashes during firmware update processes
Network Indicators:
- Unexpected firmware update traffic to devices
- Attempts to access firmware update interfaces from unauthorized sources
SIEM Query:
Example: 'firmware_update AND (buffer_overflow OR memory_corruption)' - adjust based on your logging capabilities🔗 References
- https://developer.arm.com/support/arm-security-updates
- https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git/
- https://tf-m-user-guide.trustedfirmware.org/docs/security/security_advisories/fwu_write_vulnerability.html
- https://www.trustedfirmware.org
- https://developer.arm.com/support/arm-security-updates
- https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git/
- https://tf-m-user-guide.trustedfirmware.org/docs/security/security_advisories/fwu_write_vulnerability.html
- https://www.trustedfirmware.org
