Full Report
Microsoft addressed a critical race condition vulnerability affecting its Windows Cloud Files Minifilter driver in October 2025. The flaw, assigned CVE-2025-55680, was originally discovered in March 2024 and represents a significant security concern for systems utilising OneDrive and similar cloud synchronisation services. Attribute Details CVE Identifier CVE-2025-55680 Vulnerability Type Race Condition (TOCTOU) Affected Component cldflt.sys […] The post Privilege Escalation Exploit Targets Windows Cloud Files Minifilter appeared first on GBHackers Security | #1 Globally Trusted Cyber Security News Platform.
Analysis Summary
# Vulnerability: Windows Cloud Files Minifilter Race Condition Leading to Privilege Escalation (CVE-2025-55680)
## CVE Details
- CVE ID: CVE-2025-55680
- CVSS Score: Not provided in the context, but noted as "critical" and leading to Privilege Escalation.
- CWE: Race Condition (TOCTOU)
## Affected Systems
- Products: Windows systems utilizing the Cloud Files Minifilter driver (relevant for OneDrive and similar cloud synchronization services).
- Versions: Not explicitly listed; systems running versions prior to the October 2025 security updates.
- Configurations: Systems with the `cldflt.sys` driver active, particularly those handling placeholder file creation.
## Vulnerability Description
This vulnerability is a Time-of-Check to Time-of-Use (TOCTOU) race condition within the Windows Cloud Files Minifilter driver (`cldflt.sys`), specifically in the `HsmpOpCreatePlaceholders()` function. The flaw arises because the kernel validates elements of a filename (checking for backslash or colon characters) before creating a placeholder file via `FltCreateFileEx2()`. An attacker can exploit a brief timing window between validation and file creation by rapidly modifying the filename string in a user-supplied buffer mapped into kernel space. This modification allows the attacker to inject path traversal characters and redirect the file creation to an arbitrary, restricted location (e.g., using junctions or symbolic links), resulting in unauthorized file creation with elevated privileges.
## Exploitation
- Status: Not explicitly stated as exploited in the wild, but the article refers to a "Privilege Escalation Exploit Targets." Exploitation potential confirmed by reports (Exodus Intelligence). PoC likely available due to the detailed technical writeup.
- Complexity: Medium (Requires precise timing and kernel memory manipulation).
- Attack Vector: Local (Implies a user already has some access to the affected system to trigger the API call).
## Impact
- Confidentiality: Potential impact if arbitrary file creation allows overwriting sensitive files or planting malicious binaries that execute with higher privileges.
- Integrity: High potential impact due to the ability to write arbitrary files into system-critical locations, leading to system modification.
- Availability: Potential impact via system instability or Denial of Service, though the primary demonstrated impact is Privilege Escalation.
## Remediation
### Patches
- Microsoft addressed this vulnerability in the **October 2025** security updates. Users should apply the corresponding patches for Windows systems running the Cloud Files Minifilter driver.
### Workarounds
- No specific workarounds were detailed in the provided text, though minimizing cloud synchronization services or restricting user privileges might reduce the attack surface until patching is implemented.
## Detection
- Detection methods focus on monitoring unusual activity related to `cldflt.sys` operations, especially rapid, sequenced calls to placeholder creation APIs (`CfCreatePlaceholders`) followed by file system write attempts during that brief kernel window.
- **Indicators of compromise (IoCs):** Successful exploitation leads to unauthorized file creation in protected directories.
## References
- Vendor Advisories: Microsoft October 2025 Security Updates.
- Relevant Links:
- Technical report referenced: hxxps://blog.exodusintel.com/2025/10/20/microsoft-windows-cloud-files-minifilter-toctou-privilege-escalation/
- Related patch context: Comparison to older patch related to CVE-2020-17136.