Windows Cloud Files Mini Filter Driver (cldflt.sys) Elevation of Privilege Vulnerability (CVE-2023-36036) Analysis & Mitigation Guide
Executive & SecOps Summary
SECOPS ASSESSMENTWindows 10, 11, and Windows Server operating systems utilizing the Cloud Files Mini Filter Driver (cldflt.sys)
Local attackers can exploit this vulnerability to execute arbitrary code in kernel mode, achieving full SYSTEM privileges (actively exploited in the wild)
Apply the latest Microsoft cumulative security updates immediately, or disable the affected driver service as a temporary workaround
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Applying the official cumulative security updates from Microsoft is the primary remediation. You can use the following PowerShell commands to check and force Windows Updates.
# Install and import the PSWindowsUpdate module to force updates
Install-Module PSWindowsUpdate -Force -Verbose
Get-WindowsUpdate -AcceptAll -Install -AutoReboot2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, you can mitigate the risk by disabling the Cloud Files Mini Filter Driver (cldflt.sys). Note that this may temporarily disable cloud file synchronization features like OneDrive.
# Disable the CldFlt service startup
Set-Service -Name 'CldFlt' -StartupType Disabled
# Stop the running driver service
Stop-Service -Name 'CldFlt' -Force3. Log Audit & IoC Verification Commands
Verify the file version of cldflt.sys to ensure the patch has been applied, and audit security logs for suspicious privilege escalation events.
# Check the file version of cldflt.sys
Get-ItemProperty -Path 'C:\Windows\System32\drivers\cldflt.sys' | Select-Object -Property VersionInfo | Format-List
# Audit Security Event Logs for Special Privilege Assigned (Event ID 4672)
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4672} -MaxEvents 50 | Select-Object TimeCreated, Message | Format-Table -WrapBlock 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-2023-36036) is a heap-based buffer overflow (CWE-122) and out-of-bounds write (CWE-787) vulnerability within the Windows Cloud Files Mini Filter Driver (cldflt.sys). The cldflt.sys driver is a critical kernel component responsible for managing virtual file synchronization for cloud storage services like OneDrive and iCloud. The root cause lies in insufficient input buffer validation when processing specific I/O Control (IOCTL) requests sent from user-mode applications, leading to kernel pool memory corruption.
2. Exploitation Mechanics & Attack Scenario
To exploit this vulnerability, an attacker must first gain local execution access with low privileges on the target system. The attacker then issues crafted API calls or IOCTL requests to the cldflt.sys driver. This triggers an out-of-bounds write, allowing the attacker to overwrite adjacent kernel memory structures or function pointers. Consequently, the attacker can execute arbitrary code within the kernel context and elevate their process token to NT AUTHORITY\SYSTEM.
3. Infrastructure & Business Impact
This vulnerability is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating active exploitation in the wild. Local Privilege Escalation (LPE) vulnerabilities are highly critical as they are frequently chained with initial access vectors (such as phishing or browser exploits) to perform lateral movement, bypass security controls, and compromise domain controllers or critical server infrastructure.
Official Vendor Advisories & References
Windows Cloud Files Mini Filter Driver Elevation of Privilege Vulnerability
Frequently Asked SecOps Questions (CVE-2023-36036)
FAQQ1. How critical is CVE-2023-36036 and is it actively exploited in the wild?
CVE-2023-36036 is rated CVSS 7.8 (HIGH) with a 30-day EPSS exploitation probability of 16.7%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2023-36036?
Primary impacted vendors include microsoft across windows, windows_server. Scope summary: Windows 10, Windows 11, and Windows Server 2016, 2019, 2022 running vulnerable versions of cldflt.sys
Q3. What temporary mitigations or workarounds exist for CVE-2023-36036 before patching?
[Mitigation] Apply the latest Microsoft cumulative security updates immediately, or disable the affected driver service as a temporary workaround 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-2023-36036
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