CVE-2025-55680
📋 TL;DR
A Time-of-Check Time-of-Use (TOCTOU) race condition vulnerability in the Windows Cloud Files Mini Filter Driver allows authenticated attackers to escalate privileges locally. This affects Windows systems with the Cloud Files feature enabled. Attackers can exploit this to gain SYSTEM-level privileges from a lower privileged account.
💻 Affected Systems
- Windows Cloud Files Mini Filter Driver
📦 What is this software?
Windows 10 1809 by Microsoft
Windows 10 21h2 by Microsoft
Windows 10 22h2 by Microsoft
Windows 11 22h2 by Microsoft
Windows 11 23h2 by Microsoft
Windows 11 24h2 by Microsoft
Windows 11 25h2 by Microsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with SYSTEM privileges, enabling installation of persistent malware, credential theft, and lateral movement across the network.
Likely Case
Local privilege escalation allowing attackers to bypass security controls, install unauthorized software, and access sensitive system resources.
If Mitigated
Limited impact with proper privilege separation, application control policies, and restricted administrative access.
🎯 Exploit Status
TOCTOU race conditions require precise timing and may be challenging to exploit reliably. Requires authenticated access to the system.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Microsoft Security Update Guide for specific KB numbers
Vendor Advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-55680
Restart Required: Yes
Instructions:
1. Apply latest Windows security updates via Windows Update. 2. For enterprise environments, deploy patches through WSUS, SCCM, or Intune. 3. Restart systems after patch installation.
🔧 Temporary Workarounds
Disable Cloud Files Mini Filter Driver
windowsTemporarily disable the vulnerable driver until patches can be applied
fltmc unload cldflt
Restrict User Privileges
allImplement least privilege principles to limit potential impact
🧯 If You Can't Patch
- Implement application control policies to prevent unauthorized privilege escalation
- Monitor for suspicious privilege escalation attempts and driver manipulation
🔍 How to Verify
Check if Vulnerable:
Check if cldflt.sys driver is loaded: 'fltmc' command should list cldflt if vulnerableCheck Version:
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"Verify Fix Applied:
Verify Windows Update history contains the relevant security update KB number📡 Detection & Monitoring
Log Indicators:
- Event ID 4697: Service installation attempts
- Suspicious driver loading events
- Privilege escalation attempts
Network Indicators:
- Unusual outbound connections following local privilege escalation
SIEM Query:
EventID=4697 OR (EventID=7045 AND ServiceName="cldflt")