CVE-2020-5953
📋 TL;DR
This vulnerability allows attackers to execute arbitrary code in System Management Mode (SMM) by exploiting a flaw in InsydeH2O UEFI firmware's System Management Interrupt handler. Successful exploitation enables privilege escalation from ring 0 (kernel) to ring -2 (SMM), potentially compromising the entire system. Organizations using affected InsydeH2O UEFI firmware versions are vulnerable.
💻 Affected Systems
- Systems using InsydeH2O UEFI firmware
📦 What is this software?
Insydeh2o by Insyde
Insydeh2o by Insyde
Insydeh2o by Insyde
Insydeh2o by Insyde
Insydeh2o by Insyde
Insydeh2o by Insyde
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with persistent firmware-level malware that survives OS reinstallation and disk replacement, enabling data theft, ransomware deployment, or system bricking.
Likely Case
Privilege escalation allowing attackers to bypass security controls, install rootkits, or maintain persistence on compromised systems.
If Mitigated
Limited impact if proper firmware updates are applied and SMM protections are enabled, though residual risk remains from unpatched systems.
🎯 Exploit Status
Exploitation requires kernel-level access (ring 0) first, making it a privilege escalation vulnerability rather than remote code execution.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified in public references
Vendor Advisory: https://www.insyde.com/security-pledge
Restart Required: Yes
Instructions:
1. Contact hardware/OEM vendor for firmware updates. 2. Download appropriate firmware update. 3. Apply update following vendor instructions. 4. Reboot system to activate new firmware.
🔧 Temporary Workarounds
Enable SMM protection features
allConfigure BIOS/UEFI settings to enable SMM protection if available
Restrict physical access
allLimit physical access to systems to prevent local exploitation
🧯 If You Can't Patch
- Isolate affected systems on segmented networks with strict access controls
- Implement endpoint detection and response (EDR) solutions to detect privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version against vendor advisories or use: dmidecode -t bios (Linux) or wmic bios get smbiosbiosversion (Windows)Check Version:
dmidecode -t bios | grep Version (Linux) or wmic bios get smbiosbiosversion (Windows)Verify Fix Applied:
Verify firmware version after update matches patched version from vendor📡 Detection & Monitoring
Log Indicators:
- Unexpected SMM handler calls
- Firmware modification attempts
- Privilege escalation patterns
Network Indicators:
- Unusual outbound connections from firmware update services
SIEM Query:
Search for firmware modification events or SMM-related alerts in security logs🔗 References
- https://cert-portal.siemens.com/productcert/pdf/ssa-306654.pdf
- https://security.netapp.com/advisory/ntap-20220222-0005/
- https://www.insyde.com/products
- https://www.insyde.com/security-pledge
- https://cert-portal.siemens.com/productcert/pdf/ssa-306654.pdf
- https://security.netapp.com/advisory/ntap-20220222-0005/
- https://www.insyde.com/products
- https://www.insyde.com/security-pledge
- https://www.kb.cert.org/vuls/id/796611
