CVE-2021-41840
📋 TL;DR
This vulnerability in Insyde InsydeH2O UEFI firmware allows attackers to execute arbitrary code in System Management Mode (SMM) through an SMM callout vulnerability in the NvmExpressDxe driver. It affects systems with InsydeH2O firmware versions containing kernel 5.0 through 5.5. Attackers with local access can potentially gain persistent control over affected systems.
💻 Affected Systems
- Systems with Insyde InsydeH2O UEFI firmware
📦 What is this software?
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, allowing attackers to bypass all security controls and maintain long-term access.
Likely Case
Local privilege escalation from user to kernel/SMM level, enabling installation of rootkits, credential theft, and persistence mechanisms that survive reboots.
If Mitigated
Limited impact if systems have secure boot enabled, SMM protections configured, and attackers lack local access, though firmware vulnerabilities remain concerning for persistence.
🎯 Exploit Status
Requires local access to the system. SMM exploitation typically requires kernel-level access first, making this a privilege escalation vulnerability rather than remote code execution.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check with hardware/OEM vendor for specific firmware updates
Vendor Advisory: https://www.insyde.com/security-pledge/SA-2022018
Restart Required: Yes
Instructions:
1. Identify your system manufacturer and model. 2. Check manufacturer's support site for BIOS/UEFI firmware updates. 3. Download and apply the firmware update following manufacturer instructions. 4. Reboot system to complete installation.
🔧 Temporary Workarounds
Enable Secure Boot
allSecure Boot helps prevent unauthorized code execution during boot process
Restrict Physical Access
allLimit physical access to systems to prevent local exploitation
🧯 If You Can't Patch
- Isolate affected systems on separate network segments with strict access controls
- Implement endpoint detection and response (EDR) solutions to detect SMM exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version in BIOS/UEFI settings or using manufacturer-specific tools. On Windows: wmic bios get smbiosbiosversion. On Linux: dmidecode -t biosCheck Version:
Windows: wmic bios get smbiosbiosversion
Linux: dmidecode -t bios | grep -i versionVerify Fix Applied:
Verify firmware version after update matches patched version from vendor advisory📡 Detection & Monitoring
Log Indicators:
- Unexpected firmware update attempts
- BIOS/UEFI modification events in system logs
- SMM-related errors or warnings
Network Indicators:
- Unusual outbound connections from firmware management interfaces
SIEM Query:
EventID=12 OR EventID=13 (System boot/restart events) combined with firmware modification indicators🔗 References
- https://cert-portal.siemens.com/productcert/pdf/ssa-306654.pdf
- https://security.netapp.com/advisory/ntap-20220217-0014/
- https://www.insyde.com/security-pledge
- https://www.insyde.com/security-pledge/SA-2022018
- https://cert-portal.siemens.com/productcert/pdf/ssa-306654.pdf
- https://security.netapp.com/advisory/ntap-20220217-0014/
- https://www.insyde.com/security-pledge
- https://www.insyde.com/security-pledge/SA-2022018
- https://www.kb.cert.org/vuls/id/796611
