Dell dbutil_2_3.sys Kernel Driver Privilege Escalation and Arbitrary Memory Read/Write Vulnerability (CVE-2021-21551)
Executive & SecOps Summary
SECOPS ASSESSMENTDell client platforms and firmware update utilities utilizing the dbutil_2_3.sys driver version 2.3
Local authenticated attackers can bypass access controls to directly read/write kernel memory, leading to full SYSTEM privilege escalation, denial of service (BSOD), or information disclosure
Immediately remediate by deleting the vulnerable dbutil_2_3.sys driver file and upgrading to the patched firmware update utility per Dell Advisory DSA-2021-088
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Follow Dell Security Advisory DSA-2021-088 to update your Dell utilities. You can trigger the Dell Command | Update CLI to apply the latest patches and remove vulnerable components using the following command:
# Force update drivers and firmware using Dell Command Update CLI
Start-Process -FilePath 'C:\Program Files\Dell\CommandUpdate\dcu-cli.exe' -ArgumentList '/applyUpdates -reboot=enable' -Wait -NoNewWindow2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, stop the vulnerable service and delete the driver file from the system to prevent exploitation:
# Stop the vulnerable dbutil_2_3 service and delete the driver file
Stop-Service -Name 'dbutil_2_3' -ErrorAction SilentlyContinue
$TargetPaths = @(
'C:\Users\*\AppData\Local\Temp\dbutil_2_3.sys',
'C:\Windows\Temp\dbutil_2_3.sys'
)
foreach ($Path in $TargetPaths) {
Get-Item $Path -ErrorAction SilentlyContinue | Remove-Item -Force -Verbose
}3. Log Audit & IoC Verification Commands
Use this PowerShell script to audit your endpoints for the presence of the vulnerable driver and its associated registry service:
# Check registry for dbutil_2_3 service registration
$RegCheck = Get-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Services\dbutil_2_3' -ErrorAction SilentlyContinue
if ($RegCheck) {
Write-Host '[WARNING] Vulnerable Dell Driver Service (dbutil_2_3) is registered.' -ForegroundColor Red
} else {
Write-Host '[OK] No registered dbutil_2_3 service found.' -ForegroundColor Green
}
# Scan disk for the vulnerable driver file
$FoundFiles = Get-ChildItem -Path 'C:\' -Filter 'dbutil_2_3.sys' -Recurse -ErrorAction SilentlyContinue
if ($FoundFiles) {
foreach ($File in $FoundFiles) {
Write-Host "[DANGER] Vulnerable driver file found at: $($File.FullName)" -ForegroundColor Red
}
} else {
Write-Host '[OK] No dbutil_2_3.sys files detected on C: drive.' -ForegroundColor Green
}Block Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2021-21551) is an insufficient access control flaw (CWE-782) within the dbutil_2_3.sys kernel driver, which is used by Dell firmware and BIOS update utilities. The driver fails to restrict access to its Input/Output Control (IOCTL) interfaces, allowing low-privileged local users to send direct commands to the kernel-level driver without administrative validation.
2. Exploitation Mechanics & Attack Scenario
An authenticated local attacker can open a handle to the driver's symbolic link (e.g., \\.\dbutil_2_3). By sending crafted IOCTL requests, the attacker can leverage the driver's exposed functions to read and write arbitrary physical or virtual memory addresses. This capability allows attackers to overwrite kernel structures, such as replacing the current process token with the SYSTEM token from ntoskrnl.exe, achieving local privilege escalation (LPE). It also enables Bring Your Own Vulnerable Driver (BYOVD) attacks to disable security agents.
3. Infrastructure & Business Impact
As a vulnerability listed in the CISA KEV catalog, this flaw has been actively exploited in the wild. Successful exploitation allows threat actors who have gained initial access to escalate privileges to SYSTEM, disable endpoint detection and response (EDR) agents, deploy ransomware, and establish persistent control over critical enterprise endpoints and servers.
Official Vendor Advisories & References
Dell dbutil_2_3.sys driver contains an insufficient access control vulnerability which may lead to escalation of privileges, denial of service, or information disclosure. Local authenticated user access is required.
Frequently Asked SecOps Questions (CVE-2021-21551)
FAQQ1. How critical is CVE-2021-21551 and is it actively exploited in the wild?
CVE-2021-21551 is rated CVSS 7.8 (HIGH) with a 30-day EPSS exploitation probability of 79.6%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2021-21551?
Primary impacted vendors include dell across dbutil_2_3.sys, dell_client_platform. Scope summary: All Dell desktops, laptops, tablets, and server update utilities containing the dbutil_2_3.sys driver version 2.3
Q3. What temporary mitigations or workarounds exist for CVE-2021-21551 before patching?
[Mitigation] Immediately remediate by deleting the vulnerable dbutil_2_3.sys driver file and upgrading to the patched firmware update utility per Dell Advisory DSA-2021-088 Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
Generate an Internal Engineering Notice or CISO Report for CVE-2021-21551
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