CVE-2021-46753
📋 TL;DR
This vulnerability allows attackers with malicious firmware (Uapp or ABL) to bypass length validation in AMD Secure Processor sensor fusion hub headers, enabling them to map memory regions and overwrite critical data structures. This could lead to loss of confidentiality and integrity of sensitive data. The vulnerability affects systems with AMD processors containing the vulnerable ASP firmware.
💻 Affected Systems
- AMD processors with ASP (AMD Secure Processor) firmware
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of AMD Secure Processor, allowing attackers to exfiltrate sensitive data, manipulate system behavior, or establish persistent firmware-level backdoors.
Likely Case
Local privilege escalation or data exfiltration from the secure processor environment, potentially compromising security features and sensitive information.
If Mitigated
Limited impact if proper firmware validation and secure boot are enforced, though some risk remains from malicious firmware.
🎯 Exploit Status
Exploitation requires ability to load malicious firmware components, which typically requires elevated privileges or compromised firmware update processes.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to AMD advisory for specific firmware versions
Vendor Advisory: https://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-4001
Restart Required: Yes
Instructions:
1. Check AMD advisory for affected products. 2. Obtain updated firmware from system/motherboard manufacturer. 3. Follow manufacturer's firmware update procedures. 4. Verify successful update through system BIOS/UEFI interface.
🔧 Temporary Workarounds
Restrict firmware update capabilities
allLimit who can perform firmware updates and ensure updates come from trusted sources only
Enable secure boot
allEnsure secure boot is enabled to prevent unauthorized firmware execution
🧯 If You Can't Patch
- Isolate affected systems from untrusted networks and users
- Implement strict access controls and monitoring for firmware update activities
🔍 How to Verify
Check if Vulnerable:
Check system/motherboard manufacturer website for security advisories regarding AMD SB-4001Check Version:
System-specific commands vary by manufacturer (e.g., dmidecode on Linux, wmic bios on Windows)Verify Fix Applied:
Verify firmware version in BIOS/UEFI settings matches patched version from manufacturer📡 Detection & Monitoring
Log Indicators:
- Unexpected firmware update attempts
- Secure processor error logs
- Failed secure boot events
Network Indicators:
- Unusual firmware update network traffic
- Unauthorized firmware source connections
SIEM Query:
Search for firmware update events from unauthorized sources or unexpected firmware version changes