CVE-2021-33627
📋 TL;DR
This vulnerability in Insyde InsydeH2O Kernel allows attackers to use invalid buffer addresses with the EFI_SMM_COMMUNICATION_PROTOCOL Communicate() function, potentially accessing SMRAM, MMIO, or OS kernel memory. It affects systems using vulnerable versions of InsydeH2O firmware. Attackers could exploit this to execute arbitrary code with System Management Mode (SMM) privileges.
💻 Affected Systems
- Insyde InsydeH2O Kernel
📦 What is this software?
Insydeh2o by Insyde
Insydeh2o by Insyde
Insydeh2o by Insyde
Insydeh2o by Insyde
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise via SMM privilege escalation leading to persistent firmware-level malware, bypassing OS security controls and allowing full control over hardware.
Likely Case
Local attackers with OS-level access could escalate privileges to SMM level, potentially installing persistent firmware implants or bypassing security mechanisms.
If Mitigated
With proper access controls and monitoring, exploitation would require local access and could be detected through abnormal SMM activity.
🎯 Exploit Status
Requires local access and knowledge of SMM exploitation techniques. No public exploits available as of current information.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel 5.0 05.09.11, 5.1 05.17.11, 5.2 05.27.11, 5.3 05.36.11, 5.4 05.44.11, 5.5 05.52.11
Vendor Advisory: https://www.insyde.com/security-pledge/SA-2022022
Restart Required: Yes
Instructions:
1. Check firmware version with manufacturer tools. 2. Download updated firmware from device manufacturer. 3. Apply firmware update following manufacturer instructions. 4. Reboot system to activate new firmware.
🔧 Temporary Workarounds
Restrict Local Access
allLimit physical and remote local access to vulnerable systems to reduce attack surface.
Enable Secure Boot
allEnsure Secure Boot is enabled to prevent unauthorized firmware modifications.
🧯 If You Can't Patch
- Isolate vulnerable systems in secure network segments with strict access controls
- Implement enhanced monitoring for SMM-related activities and privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version using manufacturer-specific tools (e.g., Insyde Flash Utility) or system BIOS/UEFI settings.Check Version:
Manufacturer-specific commands vary by system; typically accessed through BIOS/UEFI setup or vendor management tools.Verify Fix Applied:
Verify firmware version matches patched versions after update and check that SMM communication validation is functioning.📡 Detection & Monitoring
Log Indicators:
- Unusual SMM communication attempts
- Failed firmware validation events
- Privilege escalation attempts to SMM level
Network Indicators:
- Not network exploitable; focus on local system monitoring
SIEM Query:
Search for events related to firmware updates, SMM access attempts, or privilege escalation from user to kernel/SMM level🔗 References
- https://cert-portal.siemens.com/productcert/pdf/ssa-306654.pdf
- https://security.netapp.com/advisory/ntap-20220222-0002/
- https://www.insyde.com/security-pledge
- https://www.insyde.com/security-pledge/SA-2022022
- https://cert-portal.siemens.com/productcert/pdf/ssa-306654.pdf
- https://security.netapp.com/advisory/ntap-20220222-0002/
- https://www.insyde.com/security-pledge
- https://www.insyde.com/security-pledge/SA-2022022
- https://www.kb.cert.org/vuls/id/796611
