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Windows Cloud Files Mini Filter Driver

CVE-2026-58613 — Windows Cloud Files Mini Filter Driver Elevation of Privilege Vulnerability

Important CVSS 7.8 EPSS 0.00447 🔬 Patch diffed 2026-07 archive

Executive Summary

Use after free in Windows Cloud Files Mini Filter Driver allows an authorized attacker to elevate privileges locally.

Overview

7.8
CVSS HIGH
Important
MS Severity
Not Exploited
MS Exploit Status
Less Likely
MS Exploit Likelihood
Category Elevation of Privilege
Weakness CWE-416: Use After Free
Released Jul 14 2026
Last Updated Jul 14 2026
Publicly Disclosed No
CISA KEV Not Listed
Known Exploits None Known
EPSS Score 0.00447 — 0.37092 percentile
NVD CVSS 7.8 HIGH — matches MSRC

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
ATTACK VECTOR
Local
ATTACK COMPLEXITY
Low
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

0.00447
probability of exploitation in the next 30 days
0.37092 percentile - updated 2026-08-14
View on FIRST.org

Affected Products

19 affected products
Product KB Article Severity Impact Restart Required
Windows 10 Version 1809 for 32-bit Systems 5099538 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 1809 for x64-based Systems 5099538 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 21H2 for 32-bit Systems 5099539 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 21H2 for ARM64-based Systems 5099539 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 21H2 for x64-based Systems 5099539 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 22H2 for 32-bit Systems 5099539 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 22H2 for ARM64-based Systems 5099539 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 22H2 for x64-based Systems 5099539 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 24H2 for ARM64-based Systems 5101650 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 24H2 for x64-based Systems 5101650 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 25H2 for ARM64-based Systems 5101650 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 25H2 for x64-based Systems 5101650 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 26H1 for ARM64-based Systems 5101649 (Security Update) Important Elevation of Privilege Yes
Windows 11 version 26H1 for x64-based Systems 5101649 (Security Update) Important Elevation of Privilege Yes
Windows Server 2019 5099538 (Security Update) Important Elevation of Privilege Yes
Windows Server 2019 (Server Core installation) 5099538 (Security Update) Important Elevation of Privilege Yes
Windows Server 2022 5099540 (Security Update) Important Elevation of Privilege Yes
Windows Server 2025 5099536 (Security Update) Important Elevation of Privilege Yes
Windows Server 2025 (Server Core installation) 5099536 (Security Update) Important Elevation of Privilege Yes

Patches

6 patches
Article Type Restart
5099538 Security Update Yes
5099539 Security Update Yes
5101650 Security Update Yes
5101649 Security Update Yes
5099540 Security Update Yes
5099536 Security Update Yes

Patch Diff

ghidriff · cldflt.sys (KB5101650)

Use-after-free in CldiStreamCompleteRequest. Feature_2089223483 (introduced May 2026) inverted the deletion order: CldiStreamDeleteRequest runs before CldiStreamCdqRELEASE, freeing the stream context pool block while still in use. Triggered via orphaned provider progress request + 60s timer expiry.

Pre-patch version 10.0.26100.8737 Download
Post-patch version 10.0.26100.8875 Download
Function Address Change Note
CldiStreamCompleteRequest 1400841bc code, length, called UAF fix — swap deletion order under Feature_2089223483 flag
CldiStreamCompleteCanceledRequest 140040c58 code, called Added CdqACQUIRE reference hold before calling CompleteRequest
CldiStreamCancelSynchronousRequest 1400409f8 code, called Added CldiCanDoNonCdqCompletion check under feature flag
View full diff report View RCA report Download PoC

Attack Path

Use-after-free on HSM_STREAM_CONTEXT - an orphaned provider request on the global timer list outlives the object it references

Attack path for CVE-2026-58613 Use-after-free on HSM_STREAM_CONTEXT - an orphaned provider request on the global timer list outlives the object it references Attacker / provider process Global request list HSM_STREAM_CONTEXT Timer DPC (60s) CfReportProviderProgress2(completed=297, total=1000) 1 CldiPortNotifyMessage -> CldiPortProcessTransfer -> CldiPortProcessReportProgress -> CldSyncReportProgress -> CldStreamReportProgress -> CldiStreamBuildProviderRequest -> CldiStreamInsertIntoGlobalRequestListNoLock. Standard user. Request stores pRequest->pStreamHandleCtx->pStreamCtx, 60s deadline armed 2 Provider process terminates without CfDisconnectSyncRoot 3 Process-exit cleanup does not drain provider-initiated progress requests. CfUnregisterSyncRoot would have completed them with STATUS_CLOUD_FILE_PROVIDER_TERMINATED (0xC000CF16); termination bypasses that path entirely. rmdir /s /q on the sync root - each close calls FltReleaseContext 4 Refcount erodes until the orphaned timer-list request holds the sole remaining reference (refcount == 1). Timer fires -> CldiStreamCompleteRequest frees before releasing 5 Feature_2089223483 (May 2026) inverted the order: CldiStreamDeleteRequest now runs before CldiStreamCdqRELEASE, so the pool block is freed while still in use. Patch restores release-before-delete. Freed paged-pool block dereferenced - UAF, attacker-timed window 6 The deletion workload controls when refcount hits 1, making the reallocation spray practical.

Derived from the patch delta: the checks added by the vendor identify which fields crossed a trust boundary unvalidated. Reachability and privilege are taken from the call chain in the RCA report.

Known Exploits

Acknowledgments

Marcin 'Icewall' Noga

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