CVE-2021-36343
📋 TL;DR
Dell BIOS contains an improper input validation vulnerability that allows a local authenticated malicious user to exploit System Management Interrupt (SMI) handlers to execute arbitrary code in SMRAM. This affects Dell client systems with vulnerable BIOS versions. Attackers need local authenticated access to exploit this vulnerability.
💻 Affected Systems
- Dell client systems including laptops, desktops, and workstations
📦 What is this software?
Latitude 12 7280 Ultrabook Firmware by Dell
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Latitude 12 Rugged Extreme 7214 Firmware by Dell
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Latitude 12 Rugged Tablet 7212 Firmware by Dell
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Latitude 13 7370 Ultrabook Firmware by Dell
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Latitude 7414 Rugged Extreme Firmware by Dell
View all CVEs affecting Latitude 7414 Rugged Extreme Firmware →
⚠️ 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 security controls and maintain persistence.
Likely Case
Local privilege escalation from standard user to kernel/system-level access, enabling installation of rootkits, credential theft, and lateral movement within the network.
If Mitigated
Limited impact with proper access controls, least privilege principles, and BIOS/UEFI security features enabled, though risk remains for compromised accounts.
🎯 Exploit Status
Requires local authenticated access and knowledge of SMI exploitation techniques. Exploitation involves manipulating System Management Mode through SMI handlers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: BIOS updates specific to each Dell model - refer to Dell advisory for exact versions
Vendor Advisory: https://www.dell.com/support/kbdoc/en-us/000193321/dsa-2021-240
Restart Required: Yes
Instructions:
1. Identify your Dell system model and current BIOS version. 2. Visit Dell Support website and download the latest BIOS update for your specific model. 3. Run the BIOS update executable with administrative privileges. 4. Follow on-screen instructions and allow system to restart. 5. Verify BIOS version after update completes.
🔧 Temporary Workarounds
Restrict Local Access
allLimit physical and remote local access to sensitive systems through strict access controls and authentication requirements.
Enable BIOS/UEFI Security Features
allEnable BIOS password protection, secure boot, and other BIOS security features to add layers of protection.
🧯 If You Can't Patch
- Implement strict least privilege access controls to limit who has local authenticated access to systems
- Enable BIOS password protection and secure boot features to add additional security layers
🔍 How to Verify
Check if Vulnerable:
Check BIOS version in system settings (F2 during boot) or using 'wmic bios get smbiosbiosversion' on Windows, then compare with Dell's advisory for your specific model.Check Version:
Windows: wmic bios get smbiosbiosversion | Linux: sudo dmidecode -s bios-versionVerify Fix Applied:
Verify BIOS version after update matches or exceeds the patched version listed in Dell advisory for your specific model.📡 Detection & Monitoring
Log Indicators:
- Unusual BIOS/UEFI update attempts
- Failed BIOS password attempts
- Suspicious SMI handler activity in system logs
Network Indicators:
- No network indicators - local exploitation only
SIEM Query:
EventID=12 OR EventID=13 (System events for BIOS/UEFI changes) OR suspicious local privilege escalation patterns