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Microsoft Brokering File System

CVE-2025-21315 — Microsoft Brokering File System Elevation of Privilege Vulnerability

Important CVSS 7.8 EPSS 0.00629 🔬 Patch diffed 2025-01 archive

Executive Summary

None

Overview

7.8
CVSS HIGH
Important
MS Severity
Not Exploited
MS Exploit Status
More Likely
MS Exploit Likelihood
Category Elevation of Privilege
Weakness CWE-416: Use After Free
Released Jan 14 2025
Last Updated Jan 14 2025
Publicly Disclosed No
CISA KEV Not Listed
Known Exploits None Known
EPSS Score 0.00629 — 0.46473 percentile
NVD CVSS 7.8 HIGH — matches MSRC

CVSS Vector

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/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
Changed
CONFIDENTIALITY
High
INTEGRITY
High
AVAILABILITY
High
EXPLOIT CODE MATURITY
Unproven
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 6.8

EPSS Score

0.00629
probability of exploitation in the next 30 days
0.46473 percentile - updated 2026-07-25
View on FIRST.org

Affected Products

5 affected products
Product KB Article Severity Impact Restart Required
Windows 11 Version 24H2 for ARM64-based Systems 5050009 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 24H2 for x64-based Systems 5050009 (Security Update) Important Elevation of Privilege Yes
Windows Server 2022, 23H2 Edition (Server Core installation) 5049984 (Security Update) Important Elevation of Privilege Yes
Windows Server 2025 5050009 (Security Update) Important Elevation of Privilege Yes
Windows Server 2025 (Server Core installation) 5050009 (Security Update) Important Elevation of Privilege Yes

Patches

2 patches
Article Type Restart
5050009 Security Update Yes
5049984 Security Update Yes

Patch Diff

ghidriff · bfs.sys (KB5050009)

Patch diff 10.0.26100.2454 -> 10.0.26100.2894

Pre-patch version 10.0.26100.2454 Download
Post-patch version 10.0.26100.2894 Download
Function Address Change Note
wil_details_IsEnabledFallback 1c0003fe8 -> 1c000405c refcount, address, calling similarity 1.0
NTOSKRNL.EXE::ExReleasePushLockExclusiveEx EXTERNAL:00000018 refcount, calling similarity 1.0
BfsCheckAndReleaseIdlePolicy 1c0004e00 -> 1c0004ea4 code, length, address, called similarity 0.61
BfsProcessSetPolicyRequest 1c0007984 -> 1c0007c08 code, length, address, called similarity 0.97
NTOSKRNL.EXE::ExAcquirePushLockExclusiveEx EXTERNAL:00000017 refcount, calling similarity 1.0
BfsGetPolicyEntry 1c0005d58 -> 1c0005f88 code, length, sig, address, called similarity 0.89
BfsProcessQueryPolicySizeRequest 1c0007748 -> 1c00079bc code, length, address, called similarity 0.65
BfsReleaseNamedPipeMapping 1c000993c -> 1c0009c2c code, length, address, called similarity 0.71
BfsProcessQueryPolicyRequest 1c0007328 -> 1c0007588 code, length, address, called similarity 0.5
NTOSKRNL.EXE::KeEnterCriticalRegion EXTERNAL:00000080 refcount, calling similarity 1.0
BfsUninitializePolicyTable 1c00085a0 -> 1c0008878 code, length, address, called similarity 0.8
BfsDeleteFileFromGlobalFileTable 1c000a284 -> 1c000a628 code, length, sig, address, called similarity 0.68
BfsInsertNotPresentPolicyEntry 1c0006314 -> 1c0006564 code, length, address, called similarity 0.94
_tlgWriteTransfer_EtwWriteTransfer 1c0001008 refcount similarity 1.0
BfsInsertPolicyEntry 1c0006604 -> 1c0006868 code, length, sig, address, called similarity 0.54
BfsPostCreateOperation 1c0001c60 code, length, called similarity 0.65
BfsCloseStorage 1c000e0fc -> 1c000e4cc refcount, address, calling similarity 0.94
NTOSKRNL.EXE::ExFreePoolWithTag EXTERNAL:0000007a refcount, calling similarity 1.0
NTOSKRNL.EXE::KeLeaveCriticalRegion EXTERNAL:00000082 refcount, calling similarity 1.0
BfsCheckAndApplyPolicy 1c00048f0 -> 1c0004970 code, length, sig, address, called similarity 0.93
BfsRemoveEntryHashTable 1c000ff54 -> 1c0010324 refcount, address, calling similarity 1.0
BfsPerformPrompt 1c000b970 -> 1c000bd20 code, length, address, called similarity 0.98
BfsRemovePolicyEntry 1c0008270 -> 1c0008510 code, length, address, called similarity 0.85
BfsGetRegistryPrefix 1c000c9cc -> 1c000cd8c code, length, address, called similarity 0.86
BfsDereferencePolicyEntryEx 1c0004fa0 -> 1c0005160 code, name, fullname, length, sig, address, called similarity 0.92
View full diff report View RCA report Download PoC

Known Exploits

Acknowledgments

hazard

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