CVE-2021-46773
📋 TL;DR
This vulnerability in AMD's ABL (AGESA Boot Loader) allows a privileged attacker to corrupt ASP (AMD Secure Processor) memory through insufficient input validation. This could lead to code execution or integrity loss on affected AMD systems. The vulnerability affects systems with specific AMD processors and firmware versions.
💻 Affected Systems
- AMD EPYC processors
- AMD Ryzen processors with AMD Secure Processor
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Privileged attacker gains arbitrary code execution on the AMD Secure Processor, potentially compromising the entire system's security foundation and enabling persistent malware.
Likely Case
Privileged attacker causes system instability, crashes, or limited code execution within the secure processor environment.
If Mitigated
With proper access controls limiting privileged access, the vulnerability remains unexploited but presents a persistent risk.
🎯 Exploit Status
Exploitation requires deep understanding of AMD Secure Processor architecture and privileged access to the system.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: AGESA firmware updates with version numbers specified in AMD-SB-4001
Vendor Advisory: https://www.amd.com/en/corporate/product-security/bulletin/AMD-SB-4001
Restart Required: Yes
Instructions:
1. Check system manufacturer's website for BIOS/UEFI updates. 2. Download appropriate firmware update for your system model. 3. Follow manufacturer's firmware update instructions carefully. 4. Reboot system to apply update.
🔧 Temporary Workarounds
Restrict privileged access
allLimit administrative/root access to only necessary personnel and systems
Implement strict access controls
allUse principle of least privilege and monitor privileged account activity
🧯 If You Can't Patch
- Isolate affected systems in secure network segments with strict access controls
- Implement enhanced monitoring for privileged account activity and system integrity checks
🔍 How to Verify
Check if Vulnerable:
Check current AGESA firmware version against patched versions listed in AMD-SB-4001 advisoryCheck Version:
On Linux: 'sudo dmidecode -t bios' or check BIOS/UEFI settings; On Windows: 'wmic bios get smbiosbiosversion' or check System InformationVerify Fix Applied:
Verify firmware version has been updated to patched version after applying manufacturer's update📡 Detection & Monitoring
Log Indicators:
- Unexpected system reboots
- BIOS/UEFI access logs showing unauthorized attempts
- Privileged account activity anomalies
Network Indicators:
- None - local exploitation only
SIEM Query:
Search for: 'privileged account access' AND ('BIOS' OR 'firmware' OR 'UEFI') AND 'unusual time' OR 'multiple failed attempts'