CVE-2023-28252 — Windows Common Log File System Driver Elevation of Privilege Vulnerability

Executive Summary

None

Overview

7.8

CVSS HIGH

Important

MS Severity

Exploited

MS Exploit Status

Exploitation Detected

MS Exploit Likelihood

Category Elevation of Privilege

Weakness CWE-122: Heap-based Buffer Overflow

Released Apr 11 2023

Last Updated Apr 11 2023

Publicly Disclosed No

CISA KEV Not Listed

Known Exploits None Known

EPSS Score 0.48973 — 0.98757 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:F/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

Functional

REMEDIATION LEVEL

Official Fix

REPORT CONFIDENCE

Confirmed

Temporal Score: 7.2

EPSS Score

0.48973

probability of exploitation in the next 30 days

0.98757 percentile - updated 2026-07-25

View on FIRST.org

Affected Products

25 affected products

Product	KB Article	Severity	Impact	Restart Required
Windows 10 for 32-bit Systems	`5025234 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 for x64-based Systems	`5025234 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1607 for 32-bit Systems	`5025228 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1607 for x64-based Systems	`5025228 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1809 for 32-bit Systems	`5025229 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1809 for ARM64-based Systems	`5025229 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 1809 for x64-based Systems	`5025229 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 20H2 for 32-bit Systems	`5025221 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 20H2 for ARM64-based Systems	`5025221 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for 32-bit Systems	`5025221 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for ARM64-based Systems	`5025221 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 21H2 for x64-based Systems	`5025221 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for 32-bit Systems	`5025221 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for ARM64-based Systems	`5025221 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 10 Version 22H2 for x64-based Systems	`5025221 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 version 21H2 for ARM64-based Systems	`5025224 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 version 21H2 for x64-based Systems	`5025224 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 22H2 for ARM64-based Systems	`5025239 (Security Update)`	Important	Elevation of Privilege	Yes
Windows 11 Version 22H2 for x64-based Systems	`5025239 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2008 for 32-bit Systems Service Pack 2 5025271 (Monthly Rollup) 5025273 (Security Only) Important Elevation of Privilege 5023755 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.0.6003.22015 Yes 5025271 5025273 Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation) 5025271 (Monthly Rollup) 5025273 (Security Only) Important Elevation of Privilege 5023755 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.0.6003.22015 Yes 5025271 5025273 Windows Server 2008 for x64-based Systems Service Pack 2 5025271 (Monthly Rollup) 5025273 (Security Only) Important Elevation of Privilege 5023755 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.0.6003.22015 Yes 5025271 5025273 Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation) 5025271 (Monthly Rollup) 5025273 (Security Only) Important Elevation of Privilege 5023755 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.0.6003.22015 Yes 5025271 5025273 Windows Server 2008 R2 for x64-based Systems Service Pack 1 5025279 (Monthly Rollup) 5025277 (Security Only) Important Elevation of Privilege 5023769 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.1.7601.26466 Yes 5025279 5025277 Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) 5025279 (Monthly Rollup) 5025277 (Security Only) Important Elevation of Privilege 5023769 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.1.7601.26466 Yes 5025279 5025277 Windows Server 2012 5025287 (Monthly Rollup) 5025272 (Security Only) Important Elevation of Privilege 5023769 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.2.9200.24216 Yes None Windows Server 2012 (Server Core installation) 5025287 (Monthly Rollup) 5025272 (Security Only) Important Elevation of Privilege 5023769 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.2.9200.24216 Yes None Windows Server 2012 R2 5025285 (Monthly Rollup) 5025288 (Security Only) Important Elevation of Privilege 5023765 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.3.9600.20919 Yes None Windows Server 2012 R2 (Server Core installation) 5025285 (Monthly Rollup) 5025288 (Security Only) Important Elevation of Privilege 5023765 Base: 7.8 Temporal: 7.2 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C 6.3.9600.20919 Yes None Windows Server 2016	`5025228 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2016 (Server Core installation)	`5025228 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2019	`5025229 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2019 (Server Core installation)	`5025229 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2022	`5025230 (Security Update)`	Important	Elevation of Privilege	Yes
Windows Server 2022 (Server Core installation)	`5025230 (Security Update)`	Important	Elevation of Privilege	Yes

Patches

7 patches

Article	Type	Restart
`5025234`	Security Update	Yes
`5025228`	Security Update	Yes
`5025229`	Security Update	Yes
`5025221`	Security Update	Yes
`5025224`	Security Update	Yes
`5025239`	Security Update	Yes
`5025230`	Security Update	Yes

Patch Diff

ghidriff · clfs.sys (KB5025239)

OOB read/write via iExtendBlock/iFlushBlock=0x13 in BLF control record. ExtendMetadataBlock and WriteMetadataBlock use these as array indices without bounds check. OOB write gives 1-byte increment primitive → CONTAINER_CONTEXT redirect → vtable hijack at 0x5000000. Fix: broad BLF validation in GetControlRecord (3x growth) + WriteMetadataBlock encode check + ValidateScratchBlockOffsets (2x growth). Gated on g_signatureOffsetsValidation. Exploited ITW by Nokoyawa ransomware.

Pre-patch version 10.0.22621.1265 Download

Post-patch version 10.0.22621.1555 Download

Function	Change	Note
`CClfsBaseFile::GetControlRecord`	code, length, address, called	3x growth (299→891 bytes). Validates iExtendBlock/iFlushBlock must be 2-3, block descriptor monotonicity, sector size consistency
`CClfsBaseFilePersisted::WriteMetadataBlock`	code, length, address, called	ClfsEncodeBlock return value now checked; write skipped on encode failure; conditional decode in cleanup
`CClfsBaseFile::ValidateScratchBlockOffsets`	code, fullname, length, sig, address, called	2x growth (743→1519 bytes). Moved to CClfsLogFcbPhysical::. Reads scratch block from disk and validates sector counts, owner page offsets, monotonicity
`CClfsBaseFile::AcquireMetadataBlock`	code, length, address, called, calling	Null pointer check after metadata block acquisition; new caller ValidateScratchBlockOffsets
`CClfsLogFcbPhysical::AppendRegion`	code, length, address	Significant restructuring for bounds checking
`ClfsDecodeBlockPrivate`	code, length, address	Sector signature validation during decode

View full diff report View RCA report Download PoC

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

Boris Larin (oct0xor)
Quan Jin with DBAPPSecurity WeBin Lab
Genwei Jiang with Mandiant

References

MSRC Advisory MITRE NVD