CriticalCVE-2023-23376

Windows Common Log File System Driver Elevation of Privilege Vulnerability (CVE-2023-23376)

Published 14.02.2023Last modified 19.08.2026In CISA KEV since 14.02.2023Sources: CVE.org, pwn.watch

What is affected, what to do

Windows Common Log File System Driver Elevation of Privilege Vulnerability

The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. Update Microsoft Windows 10 Version 1507 to version 10.0.10240.19747, Microsoft Windows 10 Version 1607 to version 10.0.14393.5717, Microsoft Windows 10 Version 1809 to version 10.0.17763.4010. Immediate actions, mitigation and detection rules are in the runbook below.

Affected: Microsoft Windows 10 Version 1507 lt 10.0.10240.0..10.0.10240.19747
Microsoft Windows 10 Version 1607 lt 10.0.14393.0..10.0.14393.5717
Microsoft Windows 10 Version 1809 lt 10.0.17763.0..10.0.17763.4010
Microsoft Windows 10 Version 20H2 lt 10.0.0..10.0.19042.2604
Microsoft Windows 10 Version 21H2 lt 10.0.19043.0..10.0.19044.2604
Microsoft Windows 10 Version 22H2 lt 10.0.19045.0..10.0.19045.2604
Microsoft Windows 11 version 21H2 lt 10.0.0..10.0.22621.1574
Microsoft Windows 11 version 22H2 lt 10.0.22621.0..10.0.22621.1265
Microsoft Windows Server 2008 Service Pack 2 lt 6.0.6003.0..6.0.6003.21915
Microsoft Windows Server 2008 R2 Service Pack 1 lt 6.1.7601.0..6.1.7601.26366
Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) lt 6.1.7601.0..6.1.7601.26366
Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) lt 6.0.6003.0..6.0.6003.21915
Microsoft Windows Server 2012 lt 6.2.9200.0..6.2.9200.24116
Microsoft Windows Server 2012 (Server Core installation) lt 6.2.9200.0..6.2.9200.24116
Microsoft Windows Server 2012 R2 lt 6.3.9600.0..6.3.9600.20821
Microsoft Windows Server 2012 R2 (Server Core installation) lt 6.3.9600.0..6.3.9600.20821
Microsoft Windows Server 2016 lt 10.0.14393.0..10.0.14393.5717
Microsoft Windows Server 2016 (Server Core installation) lt 10.0.14393.0..10.0.14393.5717
Microsoft Windows Server 2019 lt 10.0.17763.0..10.0.17763.4010
Microsoft Windows Server 2019 (Server Core installation) lt 10.0.17763.0..10.0.17763.4010
Microsoft Windows Server 2022 lt 10.0.20348.0..10.0.20348.1547
Fixed in: Microsoft Windows 10 Version 1507 10.0.10240.19747
Microsoft Windows 10 Version 1607 10.0.14393.5717
Microsoft Windows 10 Version 1809 10.0.17763.4010
Microsoft Windows 10 Version 20H2 10.0.19042.2604
Microsoft Windows 10 Version 21H2 10.0.19044.2604
Microsoft Windows 10 Version 22H2 10.0.19045.2604
Microsoft Windows 11 version 21H2 10.0.22621.1574
Microsoft Windows 11 version 22H2 10.0.22621.1265
Microsoft Windows Server 2008 Service Pack 2 6.0.6003.21915
Microsoft Windows Server 2008 R2 Service Pack 1 6.1.7601.26366
Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) 6.1.7601.26366
Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) 6.0.6003.21915
Microsoft Windows Server 2012 6.2.9200.24116
Microsoft Windows Server 2012 (Server Core installation) 6.2.9200.24116
Microsoft Windows Server 2012 R2 6.3.9600.20821
Microsoft Windows Server 2012 R2 (Server Core installation) 6.3.9600.20821
Microsoft Windows Server 2016 10.0.14393.5717
Microsoft Windows Server 2016 (Server Core installation) 10.0.14393.5717
Microsoft Windows Server 2019 10.0.17763.4010
Microsoft Windows Server 2019 (Server Core installation) 10.0.17763.4010
Microsoft Windows Server 2022 10.0.20348.1547

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Metrics

7.8

Priority

XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

Source: NVD, CVSS v3

7.8

CVSS v3

Severity High on the scale from 0 to 10.

Source: CVE.org, pwn.watch

10.9 %

EPSS score

Elevated — model estimates 10-50% exploitation likelihood.

Source: FIRST EPSS, percentile 95.9

Show all metrics

Severity: Critical
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 239.68 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: actively exploited
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 7.8 Methodology
CVSS v3 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 7.8
EPSS score The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“. Read in glossary: 10.9 %; Elevated — model estimates 10-50% exploitation likelihood.
EPSS percentile The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking. Read in glossary: 95.9; Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: Actively exploited
Published: 14.02.2023
In CISA KEV since The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: 14.02.2023
CISA assessment (SSVC): Exploitation: active · not automatable · Technical impact: total; Source: CISA Vulnrichment, as of 9 February 2023
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-122

Response and mitigation

Why act now?

Prioritisation rationale

CVE-2023-23376 was exploited as a zero-day around its patch release and has been on KEV since February 2023, with CISA flagging known ransomware use. It is not network-reachable, but requires only low local privileges, no user interaction and low attack complexity — making it a dependable second-stage step for turning a phishing foothold or compromised user account into SYSTEM, then disabling security tooling and harvesting credentials. Exploitation likelihood is high, well above most published CVEs. For organisations with large Windows client estates, RDS farms or VDI, treat it as high priority and close it within your emergency patch window; given the fix has been available for a long time, any remaining unpatched host is first and foremost a patch-management finding.

01
Runbook step 1
Immediate response (0-24 h)
- Deploy the February 2023 cumulative security update (Patch Tuesday, 14 Feb 2023) or any later cumulative update. Per the context, the following builds are the boundary versions; anything below is affected: Windows 10 1507 → 10.0.10240.19747, 1607 → 10.0.14393.5717, 1809 → 10.0.17763.4010, 20H2 → 10.0.19042.2604, 21H2 → 10.0.19044.2604, 22H2 → 10.0.19045.2604; Windows 11 21H2 → 10.0.22000.1574, 22H2 → 10.0.22621.1265. Look up the exact KB per edition in the Microsoft Security Update Guide entry for CVE-2023-23376, and check Server editions there as well.
- Measure patch compliance: pull CurrentBuild + UBR from HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion via Intune/SCCM/WSUS reporting and compare against the boundary builds above. Raise high-priority tickets for anything below.
- Patch multi-user and high-exposure hosts first: RDS/terminal servers, VDI pools, jump hosts, admin workstations and general user clients with mail/browser access — where low-privilege local footholds are most likely.
- Rule out active compromise: if you see ransomware precursors (unexpected SYSTEM processes spawned from user context, new services, LSASS access), isolate the host via EDR and rotate local admin and cached domain credentials.
- Document exceptions: move hosts that cannot be patched quickly (OT-adjacent clients, legacy kit) into a time-boxed risk acceptance and enforce the compensating controls below.
02
Runbook step 2
Mitigation layers
- Restrict initial access (network/perimeter): the bug needs local code execution, so harden the routes in — block internet-sourced macros, filter ISO/IMG/LNK attachments at the mail gateway, expose RDP only via VPN/jump host with MFA.
- Application control (endpoint hardening): WDAC or AppLocker policies that deny unsigned binaries from user-writable paths (%TEMP%, %APPDATA%, C:\Users\Public, Downloads) — public CLFS exploits are typically dropped there as standalone EXE/DLL.
- Defender ASR rules: enable "Block executable files from running unless they meet a prevalence, age, or trusted list criterion", "Block credential stealing from the Windows local security authority subsystem" and "Block process creations originating from PSExec and WMI commands" to cut post-escalation activity.
- Least privilege / IAM: remove local admin rights, deploy Windows LAPS, enable Credential Guard and LSA protection (RunAsPPL) so SYSTEM on a workstation does not translate directly into domain compromise.
- Tiering: prevent privileged domain accounts from logging on to unpatched workstations (Tier 0/1 separation, "Deny log on locally" via GPO).
03
Runbook step 3
Detection rules
- Sysmon EID 11 / EDR file events: creation of .blf files or CLFS containers outside normal paths (C:\Windows\System32\config\, C:\Windows\System32\LogFiles\) by non-system processes. KQL sketch: DeviceFileEvents | where FileName endswith ".blf" and not(FolderPath has_any ("\\System32\\config\\","\\System32\\LogFiles\\")) and InitiatingProcessAccountName !~ "system"
- Process ancestry (Sysmon EID 1 / Security 4688): a process running as NT AUTHORITY\SYSTEM / IntegrityLevel=System whose parent runs as a standard user at Medium integrity (e.g. cmd.exe/powershell.exe as SYSTEM under an EXE in %TEMP%). Sigma shape: ParentUser != SYSTEM AND User == SYSTEM AND ParentImage NOT IN (services.exe, svchost.exe, wininit.exe).
- clfs.sys crashes: failed exploit attempts often bugcheck — System log Event ID 1001 (BugCheck) or 41 (Kernel-Power) with CLFS.SYS in the minidump; repeated occurrences on one host warrant investigation.
- Post-escalation behaviour: Sysmon EID 10 with TargetImage=lsass.exe from unusual processes, Security 7045/4697 (new service install), vssadmin delete shadows / wbadmin delete catalog as classic ransomware staging.

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

Windows Common Log File System Driver Elevation of Privilege Vulnerability

Source: CISA KEV Catalog, NVD (NIST), CVE.org (MITRE), pwn.watch, cvelistv5

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
Microsoft	Windows 10 Version 1507	`10.0.10240.0 – < 10.0.10240.19747`	`10.0.10240.19747`
Microsoft	Windows 10 Version 1607	`10.0.14393.0 – < 10.0.14393.5717`	`10.0.14393.5717`
Microsoft	Windows 10 Version 1809	`10.0.17763.0 – < 10.0.17763.4010`	`10.0.17763.4010`
Microsoft	Windows 10 Version 20H2	`10.0.0 – < 10.0.19042.2604`	`10.0.19042.2604`
Microsoft	Windows 10 Version 21H2	`10.0.19043.0 – < 10.0.19044.2604`	`10.0.19044.2604`
Microsoft	Windows 10 Version 22H2	`10.0.19045.0 – < 10.0.19045.2604`	`10.0.19045.2604`
Microsoft	Windows 11 version 21H2	`10.0.0 – < 10.0.22621.1574`	`10.0.22621.1574`
Microsoft	Windows 11 version 22H2	`10.0.22621.0 – < 10.0.22621.1265`	`10.0.22621.1265`
Microsoft	Windows Server 2008 R2 Service Pack 1	`6.1.7601.0 – < 6.1.7601.26366`	`6.1.7601.26366`
Microsoft	Windows Server 2008 R2 Service Pack 1 (Server Core installation)	`6.1.7601.0 – < 6.1.7601.26366`	`6.1.7601.26366`
Microsoft	Windows Server 2008 Service Pack 2	`6.0.6003.0 – < 6.0.6003.21915`	`6.0.6003.21915`
Microsoft	Windows Server 2008 Service Pack 2 (Server Core installation)	`6.0.6003.0 – < 6.0.6003.21915`	`6.0.6003.21915`
Microsoft	Windows Server 2012	`6.2.9200.0 – < 6.2.9200.24116`	`6.2.9200.24116`
Microsoft	Windows Server 2012 (Server Core installation)	`6.2.9200.0 – < 6.2.9200.24116`	`6.2.9200.24116`
Microsoft	Windows Server 2012 R2	`6.3.9600.0 – < 6.3.9600.20821`	`6.3.9600.20821`
Microsoft	Windows Server 2012 R2 (Server Core installation)	`6.3.9600.0 – < 6.3.9600.20821`	`6.3.9600.20821`
Microsoft	Windows Server 2016	`10.0.14393.0 – < 10.0.14393.5717`	`10.0.14393.5717`
Microsoft	Windows Server 2016 (Server Core installation)	`10.0.14393.0 – < 10.0.14393.5717`	`10.0.14393.5717`
Microsoft	Windows Server 2019	`10.0.17763.0 – < 10.0.17763.4010`	`10.0.17763.4010`
Microsoft	Windows Server 2019 (Server Core installation)	`10.0.17763.0 – < 10.0.17763.4010`	`10.0.17763.4010`
Microsoft	Windows Server 2022	`10.0.20348.0 – < 10.0.20348.1547`	`10.0.20348.1547`

Vendors and products

Affected operating systems

Affected operating systems

Windows	microsoft	windows_10_1507	—
Windows	microsoft	windows_10_1607	—
Windows	microsoft	windows_10_1809	—
Windows	microsoft	windows_10_20h2	—
Windows	microsoft	windows_10_21h2	—
Windows	microsoft	windows_10_22h2	—
Windows	microsoft	windows_11_21h2	—
Windows	microsoft	windows_11_22h2	—
Windows	microsoft	windows_server_2008	`r2`
Windows	microsoft	windows_server_2008	—
Windows	microsoft	windows_server_2012	`r2`
Windows	microsoft	windows_server_2012	—
Windows	microsoft	windows_server_2016	—
Windows	microsoft	windows_server_2019	—
Windows	microsoft	windows_server_2022	—

Weakness classes (CWE)

CWE-122Heap-based Buffer Overflow
Variant
A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
Entry at MITRE CWE-122

Public exploit references

Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

Public exploit references

CISA KEV Catalog	CISA Known Exploited Vulnerability (opens in a new tab)cisa.gov	actively exploited	14.02.2023

References & sources

Microsoft Security Update GuideWindows Common Log File System Driver Elevation of Privilege VulnerabilityVendor advisory, Patch
cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2023-23376government-resource
pwn.watchpwn.watch: Microsoft Windows: 2 exploited vulnerabilities (CVE-2023-21823, CVE-2023-23376)pwn-watch
Microsoft Security Update GuideVendor advisory: Microsoft Windowspwn-watch
NVD (NIST)NVD: CVE-2023-21823pwn-watch
Microsoft Security Update GuideVendor advisory: Microsoft Windowspwn-watch
NVD (NIST)NVD: CVE-2023-23376pwn-watch
cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

19.08.2026Record modifiedMicrosoft

1 individual change: Affected versions (publisher)

Show the original change

Individual changes of this event as published by NVD
Type	Action	Before	After
Affected versions (publisher)	changed	Windows 10 Version 1809, Windows 10 Version 1809, Windows Server 2019 (+20)	Windows 10 Version 1507, Windows 10 Version 1607, Windows 10 Version 1809 (+20)

Source identifier: secure@microsoft.com

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<a href="https://intel.neosec.eu/en/cve/CVE-2023-23376"><img src="https://intel.neosec.eu/badge/cve/CVE-2023-23376.svg?lang=en" alt="CVE-2023-23376 – NEOSEC Intel" height="20"></a>

What is affected, what to do

Metrics

Response and mitigation

Prioritisation rationale

Immediate response (0-24 h)

Mitigation layers

Detection rules

Detection rules

Classification under NIS2 and CRA

Description

Affected products

Vendors and products

Affected operating systems

Weakness classes (CWE)

Public exploit references

References & sources

Changes to this CVE