Windows Cloud Files Mini Filter Driver Use-After-Free Local Privilege Escalation Vulnerability (CVE-2025-62221) Urgent Security Advisory
Executive & SecOps Summary
SECOPS ASSESSMENTWindows operating systems utilizing the Windows Cloud Files Mini Filter Driver (cldflt.sys)
Local authorized attackers can corrupt kernel memory to elevate privileges to SYSTEM and execute arbitrary code
Immediately apply the official Microsoft security updates and monitor mini-filter driver activities
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Deploy the latest Microsoft Cumulative Update (LCU) to remediate this vulnerability. You can force the update process via PowerShell.
# Install Windows Update module and apply all pending security patches
Install-Module PSWindowsUpdate -Force -SkipPublisherCheck
Get-WindowsUpdate -AcceptAll -Install -AutoReboot2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, mitigate the risk by disabling the start configuration of the cldflt driver. Note that this may impact cloud file syncing features like OneDrive.
# Disable the cldflt driver service start type
Set-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Services\CldFlt' -Name 'Start' -Value 4
# Verify active filters after system reboot
fltmc filters3. Log Audit & IoC Verification Commands
Check the file version of cldflt.sys and inspect system logs for any anomalous driver behavior.
# Retrieve the file version of cldflt.sys
Get-ItemProperty -Path 'C:\Windows\System32\drivers\cldflt.sys' | Select-Object -Property VersionInfo | Format-List
# Query System Event Logs for FilterManager events related to cldflt
Get-WinEvent -FilterHashtable @{LogName='System'; ProviderName='Microsoft-Windows-FilterManager'} -ErrorAction SilentlyContinue | Where-Object {$_.Message -like '*cldflt*'}Block Exploits Instantly with Managed Virtual Patching Rules
Can't patch production immediately? Deploy managed WAF rules at the edge to intercept RCE, SQLi, and deserialization payloads before they hit your origin server.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability is a Use-After-Free (UAF, CWE-416) flaw residing within the Windows Cloud Files Mini Filter Driver (cldflt.sys). During the handling of Cloud Files API operations and synchronization contexts, the driver fails to properly manage object reference counts. This leads to a scenario where the system references a memory address that has already been deallocated, resulting in kernel pool corruption.
2. Exploitation Mechanics & Attack Scenario
To exploit this vulnerability, an attacker must first establish local execution capabilities with low-privilege access on the target system. The attacker then issues crafted Input/Output Control (IOCTL) requests to the Cloud Files Mini Filter Driver to trigger premature object deallocation. By reclaiming the freed memory space with controlled data (e.g., via heap spraying), the attacker forces the driver to reuse the corrupted object, hijacking the kernel execution flow to run arbitrary code with SYSTEM privileges.
3. Infrastructure & Business Impact
This vulnerability is actively exploited in the wild and is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog. Local Privilege Escalation (LPE) vulnerabilities are critical components of multi-stage attacks, often leveraged after initial access to disable endpoint detection and response (EDR) agents, dump credentials, and deploy ransomware across the enterprise network.
Official Vendor Advisories & References
Use after free in Windows Cloud Files Mini Filter Driver allows an authorized attacker to elevate privileges locally.
Frequently Asked SecOps Questions (CVE-2025-62221)
FAQQ1. How critical is CVE-2025-62221 and is it actively exploited in the wild?
CVE-2025-62221 is rated CVSS 7.8 (HIGH) with a 30-day EPSS exploitation probability of 2.5%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2025-62221?
Primary impacted vendors include microsoft across windows. Scope summary: Windows 10, 11, and Windows Server editions running the Windows Cloud Files Mini Filter Driver (cldflt.sys)
Q3. What temporary mitigations or workarounds exist for CVE-2025-62221 before patching?
[Mitigation] Immediately apply the official Microsoft security updates and monitor mini-filter driver activities 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-2025-62221
Instantly format this advisory into an executive CISO summary or engineering patch ticket.
🔗 Related Advisories in Similar Stack (microsoft)
View Category →Windows AFD.sys Use-After-Free Local Privilege Escalation Vulnerability (CVE-2026-68820) Security Advisory
[Affected Scope] Systems running Microsoft Windows operating systems utilizing the Ancillary Function Driver for WinSock (afd.sys)
Windows IKE Extension Double Free Remote Code Execution Vulnerability (CVE-2026-33824)
[Affected Scope] Internet Key Exchange (IKE) Extension service running on Microsoft Windows and Windows Server operating systems
Microsoft MSHTML Framework Security Feature Bypass Vulnerability (CVE-2026-21513) Analysis and Mitigation Guide
[Affected Scope] Applications and system components utilizing the MSHTML (Trident) engine within Microsoft Windows environments
Microsoft Windows Shell Security Feature Bypass Vulnerability (CVE-2026-21510) Urgent Security Advisory
[Affected Scope] Windows Shell component across Microsoft Windows operating systems
Subscribe to Daily Vulnerability Briefings & KEV Alerts
Concise morning briefings for SecOps, DevSecOps, and SRE teams covering newly exploited CVEs and mitigation priorities.