OnlyPatch
Windows Common Log File System Driver

CVE-2025-62470 — Windows Common Log File System Driver Elevation of Privilege Vulnerability

Important CVSS 7.8 EPSS 0.00496 🔬 Patch diffed 2025-12 archive

Executive Summary

Heap-based buffer overflow in Windows Common Log File System Driver allows an authorized attacker to elevate privileges locally.

Overview

7.8
CVSS HIGH
Important
MS Severity
Not Exploited
MS Exploit Status
More Likely
MS Exploit Likelihood
Category Elevation of Privilege
Weakness CWE-122: Heap-based Buffer Overflow
Released Dec 9 2025
Last Updated Dec 9 2025
Publicly Disclosed No
CISA KEV Not Listed
Known Exploits None Known
EPSS Score 0.00496 — 0.40208 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

0.00496
probability of exploitation in the next 30 days
0.40208 percentile - updated 2026-08-14
View on FIRST.org

Affected Products

21 affected products
Product KB Article Severity Impact Restart Required
Windows 10 Version 1607 for 32-bit Systems 5071543 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 1607 for x64-based Systems 5071543 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 1809 for 32-bit Systems 5071544 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 1809 for x64-based Systems 5071544 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 21H2 for 32-bit Systems 5071546 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 21H2 for ARM64-based Systems 5071546 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 21H2 for x64-based Systems 5071546 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 22H2 for 32-bit Systems 5071546 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 22H2 for ARM64-based Systems 5071546 (Security Update) Important Elevation of Privilege Yes
Windows 10 Version 22H2 for x64-based Systems 5071546 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 23H2 for ARM64-based Systems 5071417 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 23H2 for x64-based Systems 5071417 (Security Update) Important Elevation of Privilege Yes
Windows 11 Version 24H2 for ARM64-based Systems 5072033 (Security Update) 5072014 (Security Hotpatch Update) Important Elevation of Privilege 5068861 5068966 Base: 7.8 Temporal: 6.8 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 10.0.26100.7462 10.0.26100.7392 Yes None Windows 11 Version 24H2 for x64-based Systems 5072033 (Security Update) 5072014 (Security Hotpatch Update) Important Elevation of Privilege 5068861 5068966 Base: 7.8 Temporal: 6.8 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 10.0.26100.7462 10.0.26100.7392 Yes None Windows 11 Version 25H2 for ARM64-based Systems 5072033 (Security Update) 5072014 (Security Hotpatch Update) Important Elevation of Privilege 5068861 5068966 Base: 7.8 Temporal: 6.8 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 10.0.26200.7462 10.0.26200.7392 Yes None Windows 11 Version 25H2 for x64-based Systems 5072033 (Security Update) 5072014 (Security Hotpatch Update) Important Elevation of Privilege 5068861 5068966 Base: 7.8 Temporal: 6.8 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 10.0.26200.7462 10.0.26200.7392 Yes None Windows Server 2008 for 32-bit Systems Service Pack 2 5071504 (Monthly Rollup) 5071507 (Security Only) Important Elevation of Privilege 5068906 Base: 7.8 Temporal: 6.8 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 6.0.6003.23666 Yes None Windows Server 2008 for 32-bit Systems Service Pack 2 (Server Core installation) 5071504 (Monthly Rollup) 5071507 (Security Only) Important Elevation of Privilege 5068906 Base: 7.8 Temporal: 6.8 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 6.0.6003.23666 Yes None Windows Server 2008 for x64-based Systems Service Pack 2 5071504 (Monthly Rollup) 5071507 (Security Only) Important Elevation of Privilege 5068906 Base: 7.8 Temporal: 6.8 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 6.0.6003.23666 Yes None Windows Server 2008 for x64-based Systems Service Pack 2 (Server Core installation) 5071504 (Monthly Rollup) 5071507 (Security Only) Important Elevation of Privilege 5068906 Base: 7.8 Temporal: 6.8 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 6.0.6003.23666 Yes None Windows Server 2008 R2 for x64-based Systems Service Pack 1 5071501 (Monthly Rollup) 5071506 (Security Only) Important Elevation of Privilege 5068904 Base: 7.8 Temporal: 6.8 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 6.1.7601.28064 Yes None Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) 5071501 (Monthly Rollup) 5071506 (Security Only) Important Elevation of Privilege 5068904 Base: 7.8 Temporal: 6.8 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 6.1.7601.28064 Yes None Windows Server 2012 5071505 (Monthly Rollup) Important Elevation of Privilege Yes
Windows Server 2012 (Server Core installation) 5071505 (Monthly Rollup) Important Elevation of Privilege Yes
Windows Server 2012 R2 5071503 (Monthly Rollup) Important Elevation of Privilege Yes
Windows Server 2012 R2 (Server Core installation) 5071503 (Monthly Rollup) Important Elevation of Privilege Yes
Windows Server 2016 5071543 (Security Update) Important Elevation of Privilege Yes
Windows Server 2016 (Server Core installation) 5071543 (Security Update) Important Elevation of Privilege Yes
Windows Server 2019 5071544 (Security Update) Important Elevation of Privilege Yes
Windows Server 2019 (Server Core installation) 5071544 (Security Update) Important Elevation of Privilege Yes
Windows Server 2022 5071547 (Security Update) 5071413 (Security Hotpatch Update) Important Elevation of Privilege 5068787 5068840 Base: 7.8 Temporal: 6.8 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 10.0.20348.4529 10.0.20348.4467 Yes None Windows Server 2022 (Server Core installation) 5071547 (Security Update) 5071413 (Security Hotpatch Update) Important Elevation of Privilege 5068787 5068840 Base: 7.8 Temporal: 6.8 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 10.0.20348.4529 10.0.20348.4467 Yes None Windows Server 2022, 23H2 Edition (Server Core installation) 5071542 (Security Update) Important Elevation of Privilege Yes

Patches

7 patches
Article Type Restart
5071543 Security Update Yes
5071544 Security Update Yes
5071546 Security Update Yes
5071417 Security Update Yes
5071505 Monthly Rollup Yes
5071503 Monthly Rollup Yes
5071542 Security Update Yes

Patch Diff

ghidriff + headless-ghidra · clfs.sys (KB5072653)

Reservation-accounting hardening on the CLFS log client-context block (CCB+0x68, ReservedLogSpace). Pre-patch WriteRestart guarded the reservation only against ADD overflow (`ReservedLogSpace + userValue < 0`); ReserveAndAppendLog set an error inline on failure. The December patch, gated behind Feature_1757897016, adds a SUBTRACTION-underflow guard (`ReservedLogSpace - amount < 0`) alongside the existing add check, and routes the reservation-accounting failures through CClfsLogFcbCommon::ReportFlushFailure(8, -0x3fffffff) instead of silently setting STATUS_INSUFFICIENT_RESOURCES. WriteRestart additionally inlines the CClfsLogCcb::MarkAccessed StateFlags update (CCB+0x1c |= 8, LOCK/UNLOCK) and splits status tracking into two accumulators. This is the same +0x68 counter released by CClfsLogCcb::Cleanup in CVE-2025-29824 and incremented by WriteRestart in CVE-2025-24059 - the third patch in a 2025 sequence hardening one reservation field. Both branches ship in 10.0.26100.7462; the unguarded path runs when the flag is off. Verified by headless-Ghidra decompilation of both builds.

Pre-patch version 10.0.26100.7309
Post-patch version 10.0.26100.7462
Function Address Change Note
CClfsRequest::WriteRestart code (2nd status accumulator + inline MarkAccessed, gated Feature_1757897016) 5295 -> 5932 chars. Adds Feature_1757897016 gate; splits the single status var into uVar7/local_78; replaces the CClfsLogCcb::MarkAccessed() call with an inline `if ((ccb->StateFlags(+0x1c) & 8)==0){LOCK; |= 8; UNLOCK}`. The +0x68 add-overflow guard (0xc01a0010) is retained.
CClfsRequest::ReserveAndAppendLog code (subtraction-underflow guard added, gated Feature_1757897016) 12665 -> 11716 chars. PRE guarded only `local_118 + ccb->ReservedLogSpace(+0x68) < 0`. POST guards BOTH `local_128 + ccb->ReservedLogSpace < 0` AND `ccb->ReservedLogSpace - local_118 < 0` - i.e. adds the subtraction-underflow case. Two inline LOCK/UNLOCK error stubs are replaced by CClfsLogFcbCommon::ReportFlushFailure(8, -0x3fffffff). New early-out `if (local_140==0 && local_128==0) goto done` under the flag.
CClfsLogCcb::MarkAccessed 14001536c NOT changed Byte-identical pre/post (277 chars). ghidriff listed it on address/refcount grounds only. The March->December MarkAccessed hypothesis is ruled out: December inlines the accessed-bit set into WriteRestart rather than modifying the helper.
CClfsLogFcbCommon::ReportFlushFailure NOT changed (new call target) Byte-identical pre/post (673 chars). It is newly CALLED from ReserveAndAppendLog's failure paths, which is why ghidriff flagged it.
Feature_1757897016__private_IsEnabledDeviceUsageNoInline / _IsEnabledFallback added -- CFR gate Both paths ship in 10.0.26100.7462.
View full diff report View RCA report

Attack Path

The log-space reservation counter is guarded against overflow on addition but not underflow on subtraction, so reserved space can be driven negative

Attack path for CVE-2025-62470 The log-space reservation counter is guarded against overflow on addition but not underflow on subtraction, so reserved space can be driven negative 01 — ENTRY Standard user creates a CLFS log and issues reserve/append and write-restart operations CreateLogFile in any user-writable directory. CLFS is a core kernel component on every install; no elevation. The client-context block (CCB) tracks how much log space this handle has reserved at CCB+0x68 (ReservedLogSpace). 02 — CONTROLLED INPUT The reserved and appended amounts are driven from the caller's requests WriteRestart takes its value from the ProbeForRead-ed user buffer (this+0xf0); ReserveAndAppendLog computes append/reserve deltas from request parameters. 03 — PATH Both paths adjust ReservedLogSpace at CCB+0x68 WriteRestart does `ReservedLogSpace += amount`; ReserveAndAppendLog reserves and consumes against the same field. 04 — MISSING CHECK Pre-patch the counter is only checked against ADD overflow, not SUBTRACT underflow WriteRestart rejects `ReservedLogSpace + userValue < 0` but nothing rejects a subtraction taking it below zero. The patch (Feature_1757897016) adds the `ReservedLogSpace - amount < 0` guard to ReserveAndAppendLog and routes failures through ReportFlushFailure(8, -0x3fffffff). 05 — PRIMITIVE Reserved log space driven negative - corrupted reservation accounting An unsigned underflow of the reservation counter mis-sizes later append/flush placement, the classic CLFS metadata-to-pool route. Third patch in the 2025 sequence hardening CCB+0x68 (with CVE-2025-24059 and the CVE-2025-29824 zero-day). Gated behind Feature_1757897016; the unguarded path still ships.

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

haowei yan(jingdong dawnslab)
0rb1t

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