CVE-2021-41838
📋 TL;DR
This vulnerability allows attackers to access System Management Mode (SMM) and execute arbitrary code in Insyde InsydeH2O UEFI firmware. It affects systems with InsydeH2O firmware versions containing vulnerable SdHostDriver in kernel 5.0 through 5.5. Attackers can potentially gain high-privilege access to the system firmware.
💻 Affected Systems
- Systems with Insyde InsydeH2O UEFI firmware
📦 What is this software?
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 firmware-level persistence, allowing attackers to bypass operating system security controls, install rootkits, and maintain access even after OS reinstallation.
Likely Case
Privilege escalation to SMM level, enabling execution of arbitrary code with highest system privileges, potentially leading to data theft, system manipulation, or installation of persistent malware.
If Mitigated
Limited impact if proper firmware security controls are enabled and systems are isolated from potential attack vectors.
🎯 Exploit Status
Exploitation requires local code execution capability. The vulnerability involves SMM callout exploitation through improper numeric range checking.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check vendor-specific firmware updates
Vendor Advisory: https://www.insyde.com/security-pledge/SA-2022023
Restart Required: Yes
Instructions:
1. Check with your system manufacturer for firmware updates. 2. Download the appropriate firmware update. 3. Apply the firmware update following manufacturer instructions. 4. Reboot the system to complete the update.
🔧 Temporary Workarounds
Restrict local code execution
allImplement strict application control policies to prevent unauthorized code execution
Enable firmware security features
allEnsure Secure Boot and other firmware security features are enabled
🧯 If You Can't Patch
- Isolate affected systems from untrusted networks and users
- Implement strict access controls and monitoring for privileged operations
🔍 How to Verify
Check if Vulnerable:
Check firmware version and kernel version in UEFI settings or using manufacturer-specific toolsCheck Version:
Manufacturer-specific commands vary; typically check in UEFI/BIOS settings or use 'dmidecode' on LinuxVerify Fix Applied:
Verify firmware version has been updated to a version after the patch release date📡 Detection & Monitoring
Log Indicators:
- Unexpected firmware access attempts
- SMM-related errors in system logs
- Unauthorized firmware modification attempts
Network Indicators:
- Unusual outbound connections from firmware management interfaces
SIEM Query:
Search for firmware update events, SMM access attempts, or unauthorized BIOS/UEFI modifications🔗 References
- https://cert-portal.siemens.com/productcert/pdf/ssa-306654.pdf
- https://security.netapp.com/advisory/ntap-20220222-0001/
- https://www.insyde.com/security-pledge
- https://www.insyde.com/security-pledge/SA-2022023
- https://cert-portal.siemens.com/productcert/pdf/ssa-306654.pdf
- https://security.netapp.com/advisory/ntap-20220222-0001/
- https://www.insyde.com/security-pledge
- https://www.insyde.com/security-pledge/SA-2022023
- https://www.kb.cert.org/vuls/id/796611
