CVE-2021-21551
📋 TL;DR
CVE-2021-21551 is a privilege escalation vulnerability in Dell's dbutil_2_3.sys driver that allows local authenticated users to read/write arbitrary kernel memory. This can lead to system compromise, denial of service, or information disclosure. Affected users are those running vulnerable Dell systems with the driver installed.
💻 Affected Systems
- Dell Client Platforms
- Dell Systems with dbutil_2_3.sys driver
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise via privilege escalation to SYSTEM/NT AUTHORITY, allowing installation of persistent malware, credential theft, and complete control of the affected system.
Likely Case
Local privilege escalation by authenticated attackers to gain administrative privileges on the system.
If Mitigated
Limited impact if proper access controls restrict local user accounts and driver loading is controlled.
🎯 Exploit Status
Multiple public proof-of-concept exploits exist demonstrating arbitrary read/write capabilities. Exploitation requires local authenticated access but is straightforward once access is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: dbutil_2_3.sys driver version with fix (updated via Dell Security Advisory DSA-2021-088)
Restart Required: Yes
Instructions:
1. Download and install Dell Security Update DSA-2021-088. 2. Update Dell firmware and drivers through Dell Command Update or SupportAssist. 3. Restart the system to apply changes.
🔧 Temporary Workarounds
Driver Removal
windowsRemove the vulnerable dbutil_2_3.sys driver from the system
sc stop dbutil_2_3
sc delete dbutil_2_3
del C:\Windows\System32\drivers\dbutil_2_3.sys
Driver Deny List
windowsPrevent loading of the vulnerable driver using Windows Driver Block Rules
reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows\Driver Security" /v "DriverBlockRules" /t REG_SZ /d "dbutil_2_3.sys" /f
🧯 If You Can't Patch
- Restrict local user account privileges and implement least privilege access controls
- Monitor for suspicious driver loading events and unauthorized privilege escalation attempts
🔍 How to Verify
Check if Vulnerable:
Check for existence of dbutil_2_3.sys driver: dir C:\Windows\System32\drivers\dbutil_2_3.sysCheck Version:
powershell Get-WmiObject Win32_PnPSignedDriver | Where-Object {$_.DeviceName -like '*dbutil*'} | Select-Object DeviceName, DriverVersionVerify Fix Applied:
Verify driver version is updated or removed, and check Dell Security Advisory DSA-2021-088 installation status📡 Detection & Monitoring
Log Indicators:
- Windows Security Event ID 4697 (Service installed)
- Driver loading events for dbutil_2_3.sys
- Unexpected privilege escalation events
Network Indicators:
- No direct network indicators - local exploitation only
SIEM Query:
EventID=4697 AND ServiceFileName="*dbutil*" OR ProcessName="*dbutil*"🔗 References
- http://packetstormsecurity.com/files/162604/Dell-DBUtil_2_3.sys-IOCTL-Memory-Read-Write.html
- http://packetstormsecurity.com/files/162739/DELL-dbutil_2_3.sys-2.3-Arbitrary-Write-Privilege-Escalation.html
- https://www.dell.com/support/kbdoc/en-us/000186019/dsa-2021-088-dell-client-platform-security-update-for-dell-driver-insufficient-access-control-vulnerability
- http://packetstormsecurity.com/files/162604/Dell-DBUtil_2_3.sys-IOCTL-Memory-Read-Write.html
- http://packetstormsecurity.com/files/162739/DELL-dbutil_2_3.sys-2.3-Arbitrary-Write-Privilege-Escalation.html
- https://www.dell.com/support/kbdoc/en-us/000186019/dsa-2021-088-dell-client-platform-security-update-for-dell-driver-insufficient-access-control-vulnerability
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-21551
