CVE-2021-33626
📋 TL;DR
This vulnerability allows attackers to corrupt SMRAM memory through insufficient validation of buffer pointers in SMM SWSMI handlers, potentially leading to arbitrary code execution. It affects systems with vulnerable UEFI firmware implementations, particularly those from Insyde Software and vendors using their code. Attackers need local access to exploit this vulnerability.
💻 Affected Systems
- Systems with Insyde Software UEFI firmware
- Siemens SIMATIC IPC products
- NetApp storage systems with affected firmware
- Various OEM systems using Insyde firmware
📦 What is this software?
Insydeh2o by Insyde
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, and system control.
Likely Case
Local privilege escalation from user to kernel or system management mode privileges, allowing attackers to bypass security controls and install persistent malware.
If Mitigated
Limited impact if proper access controls prevent local attacker access and firmware integrity protections are enabled.
🎯 Exploit Status
Exploitation requires deep knowledge of UEFI/SMM internals and physical or administrative access. No public exploits known as of knowledge cutoff.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Varies by vendor; check specific vendor advisories for patched firmware versions
Vendor Advisory: https://www.insyde.com/security-pledge/SA-2021001
Restart Required: Yes
Instructions:
1. Identify system manufacturer and model. 2. Check vendor website for BIOS/UEFI firmware updates. 3. Download appropriate firmware update. 4. Follow vendor-specific flashing instructions (usually requires reboot). 5. Verify successful update in BIOS/UEFI setup.
🔧 Temporary Workarounds
Restrict physical and administrative access
allLimit who can physically access systems or obtain administrative privileges
Enable firmware integrity protections
allEnable Secure Boot and other firmware protection features if available
🧯 If You Can't Patch
- Implement strict access controls to prevent unauthorized local access to affected systems
- Monitor for suspicious firmware modification attempts and privilege escalation activities
🔍 How to Verify
Check if Vulnerable:
Check system firmware version against vendor advisories; use 'wmic bios get smbiosbiosversion' on Windows or 'dmidecode -t bios' on LinuxCheck Version:
Windows: wmic bios get smbiosbiosversion | Linux: dmidecode -t bios | grep VersionVerify Fix Applied:
Verify firmware version after update matches patched version from vendor advisory📡 Detection & Monitoring
Log Indicators:
- Unexpected firmware update attempts
- Privilege escalation from user to SYSTEM/admin
- Suspicious SMM-related activity
Network Indicators:
- None - this is a local exploit
SIEM Query:
EventID=6005 (Event log service started) followed by privilege escalation events, or firmware update logs from vendor-specific sources🔗 References
- https://cert-portal.siemens.com/productcert/pdf/ssa-306654.pdf
- https://security.netapp.com/advisory/ntap-20220216-0006/
- https://www.insyde.com/security-pledge
- https://www.insyde.com/security-pledge/SA-2021001
- https://cert-portal.siemens.com/productcert/pdf/ssa-306654.pdf
- https://security.netapp.com/advisory/ntap-20220216-0006/
- https://www.insyde.com/security-pledge
- https://www.insyde.com/security-pledge/SA-2021001
- https://www.kb.cert.org/vuls/id/796611
