Windows Cloud Files Mini Filter Driver
CVE-2025-55680 — Windows Cloud Files Mini Filter Driver Elevation of Privilege Vulnerability
Executive Summary
Time-of-check time-of-use (toctou) race condition in Windows Cloud Files Mini Filter Driver allows an authorized attacker to elevate privileges locally.
Overview
7
CVSS HIGH
Important
MS Severity
Not Exploited
MS Exploit Status
More Likely
MS Exploit Likelihood
CVSS Vector
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
ATTACK VECTOR
Local
ATTACK COMPLEXITY
High
PRIVILEGES REQUIRED
Low
USER INTERACTION
None
SCOPE
Unchanged
CONFIDENTIALITY
High
INTEGRITY
High
AVAILABILITY
High
EXPLOIT CODE MATURITY
Unproven
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 6.8
EPSS Score
0.0043
probability of exploitation in the next 30 days
0.35236 percentile - updated 2026-07-25
View on FIRST.org
Affected Products
23 affected products
| Product | KB Article | Severity | Impact | Restart Required |
|---|---|---|---|---|
| Windows 10 Version 1809 for 32-bit Systems | 5066586 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 1809 for x64-based Systems | 5066586 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 21H2 for 32-bit Systems | 5066791 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 21H2 for ARM64-based Systems | 5066791 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 21H2 for x64-based Systems | 5066791 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 22H2 for 32-bit Systems | 5066791 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 22H2 for ARM64-based Systems | 5066791 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 10 Version 22H2 for x64-based Systems | 5066791 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 11 Version 22H2 for ARM64-based Systems | 5066793 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 11 Version 22H2 for x64-based Systems | 5066793 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 11 Version 23H2 for ARM64-based Systems | 5066793 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 11 Version 23H2 for x64-based Systems | 5066793 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 11 Version 24H2 for ARM64-based Systems | 5066835 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 11 Version 24H2 for x64-based Systems | 5066835 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 11 Version 25H2 for ARM64-based Systems | 5066835 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows 11 Version 25H2 for x64-based Systems | 5066835 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server 2019 | 5066586 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server 2019 (Server Core installation) | 5066586 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server 2022 | 5066782 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server 2022 (Server Core installation) | 5066782 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server 2022, 23H2 Edition (Server Core installation) | 5066780 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server 2025 | 5066835 (Security Update) |
Important | Elevation of Privilege | Yes |
| Windows Server 2025 (Server Core installation) | 5066835 (Security Update) |
Important | Elevation of Privilege | Yes |
Patches
6 patches
| Article | Type | Restart |
|---|---|---|
5066586 |
Security Update | Yes |
5066791 |
Security Update | Yes |
5066793 |
Security Update | Yes |
5066835 |
Security Update | Yes |
5066782 |
Security Update | Yes |
5066780 |
Security Update | Yes |
Patch Diff
ghidriff + GhidraMCP verification · cldflt.sys (KB5066835)
TOCTOU race (CWE-367) in cldflt.sys HsmpOpCreatePlaceholders (IOCTL 0x903BC / CfCreatePlaceholders): the placeholder relName is validated for '\' and ':' while still living in a userspace buffer mapped into kernel VA via IoAllocateMdl+MmProbeAndLockPages+MmMapLockedPagesSpecifyCache (shared physical pages). A racing thread flips one wide char 'D'->'\' between validation and FltCreateFileEx2, so the create resolves through an attacker-planted junction inside the attacker's own sync root into a protected directory (e.g. C:\Windows\System32) — arbitrary file/directory creation as SYSTEM, leveraged for DLL side-loading privesc (Exodus Intelligence, patched October 2025 KB5066835). VERIFIED 2026-07-20 via GhidraMCP: fix snapshots the payload into kernel pool behind Feature_4257790267 (ExAllocatePool2+memcpy) so validate and use both read the private copy.
| Function | Address | Change | Note |
|---|---|---|---|
cldflt!HsmpOpCreatePlaceholders |
0x14005e934 (pre) / 0x14005e954 (post) |
code (verified via GhidraMCP 2026-07-20) | TOCTOU: relName validated ('\' 0x5C / ':' 0x3A scan) and then consumed by FltCreateFileEx2 directly from an MmMapLockedPagesSpecifyCache-mapped USERSPACE buffer; attacker thread flips 'D'->'\' between check and use so the create follows an attacker junction (e.g. JUSTASTRING -> C:\Windows\System32) => arbitrary file/dir creation as SYSTEM. Fix: behind new WIL flag Feature_4257790267, the entire payload is snapshotted into a private pool buffer (ExAllocatePool2 NonPagedPoolNx + ProbeForWrite + memcpy) and both the scan and ObjectName use the snapshot; results memcpy'd back on success. |
Feature_4257790267__private_IsEnabledDeviceUsageNoInline (+ fallback/reporting) |
|
added | New CFR kill-switch gating the pool-snapshot path; legacy MDL path remains compiled in behind the flag |
cldflt!HsmFltProcessCreatePlaceholders (caller) |
|
context (unchanged) | IOCTL 0x903BC (Tag 0x9000001A=IO_REPARSE_TAG_CLOUD, OpType 0xC0000001) dispatch via HsmFltPreFILE_SYSTEM_CONTROL -> HsmiOpPrepareOperation; size checks nInBufferSize>=0x20, payload>=0x50 |
Known Exploits
No known exploits have been linked for this CVE yet. When available, exploit references will be sourced from public repositories and may be unverified, incomplete, or non-functional. Always review code carefully before use in any environment.
Acknowledgments
References
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