CriticalCVE-2025-32701

    Windows Common Log File System Driver Elevation of Privilege Vulnerability (CVE-2025-32701)

    Published In CISA KEV since Sources: pwn.watch, CVE.org, Msrc Update Guide

    What is affected, what to do

    Use after free in Windows Common Log File System Driver allows an authorized attacker to elevate privileges locally.

    The vulnerability is being actively exploited; treat it as a priority. Update Microsoft Windows 10 Version 1507 to version 10.0.10240.21014, Microsoft Windows 10 Version 1607 to version 10.0.14393.8066, Microsoft Windows 10 Version 1809 to version 10.0.17763.7314. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Microsoft Windows 10 Version 1507 lt 10.0.10240.0..10.0.10240.21014
    • Microsoft Windows 10 Version 1607 lt 10.0.14393.0..10.0.14393.8066
    • Microsoft Windows 10 Version 1809 lt 10.0.17763.0..10.0.17763.7314
    • Microsoft Windows 10 Version 21H2 lt 10.0.19044.0..10.0.19044.5854
    • Microsoft Windows 10 Version 22H2 lt 10.0.19045.0..10.0.19045.5854
    • Microsoft Windows 11 version 22H2 lt 10.0.22621.0..10.0.22621.5335
    • Microsoft Windows 11 version 22H3 lt 10.0.22631.0..10.0.22631.5335
    • Microsoft Windows 11 Version 23H2 lt 10.0.22631.0..10.0.22631.5335
    • Microsoft Windows 11 Version 24H2 lt 10.0.26100.0..10.0.26100.4061
    • Microsoft Windows Server 2008 R2 Service Pack 1 lt 6.1.7601.0..6.1.7601.27729
    • Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) lt 6.1.7601.0..6.1.7601.27729
    • Microsoft Windows Server 2008 Service Pack 2 lt 6.0.6003.0..6.0.6003.23279
    • Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) lt 6.0.6003.0..6.0.6003.23279
    • Microsoft Windows Server 2012 lt 6.2.9200.0..6.2.9200.25475
    • Microsoft Windows Server 2012 (Server Core installation) lt 6.2.9200.0..6.2.9200.25475
    • Microsoft Windows Server 2012 R2 lt 6.3.9600.0..6.3.9600.22577
    • Microsoft Windows Server 2012 R2 (Server Core installation) lt 6.3.9600.0..6.3.9600.22577
    • Microsoft Windows Server 2016 lt 10.0.14393.0..10.0.14393.8066
    • Microsoft Windows Server 2016 (Server Core installation) lt 10.0.14393.0..10.0.14393.8066
    • Microsoft Windows Server 2019 lt 10.0.17763.0..10.0.17763.7314
    • Microsoft Windows Server 2019 (Server Core installation) lt 10.0.17763.0..10.0.17763.7314
    • Microsoft Windows Server 2022 lt 10.0.20348.0..10.0.20348.3692
    • Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) lt 10.0.25398.0..10.0.25398.1611
    • Microsoft Windows Server 2025 lt 10.0.26100.0..10.0.26100.4061
    • Microsoft Windows Server 2025 (Server Core installation) lt 10.0.26100.0..10.0.26100.4061
    Fixed in
    • Microsoft Windows 10 Version 1507 10.0.10240.21014
    • Microsoft Windows 10 Version 1607 10.0.14393.8066
    • Microsoft Windows 10 Version 1809 10.0.17763.7314
    • Microsoft Windows 10 Version 21H2 10.0.19044.5854
    • Microsoft Windows 10 Version 22H2 10.0.19045.5854
    • Microsoft Windows 11 version 22H2 10.0.22621.5335
    • Microsoft Windows 11 version 22H3 10.0.22631.5335
    • Microsoft Windows 11 Version 23H2 10.0.22631.5335
    • Microsoft Windows 11 Version 24H2 10.0.26100.4061
    • Microsoft Windows Server 2008 R2 Service Pack 1 6.1.7601.27729
    • Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) 6.1.7601.27729
    • Microsoft Windows Server 2008 Service Pack 2 6.0.6003.23279
    • Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) 6.0.6003.23279
    • Microsoft Windows Server 2012 6.2.9200.25475
    • Microsoft Windows Server 2012 (Server Core installation) 6.2.9200.25475
    • Microsoft Windows Server 2012 R2 6.3.9600.22577
    • Microsoft Windows Server 2012 R2 (Server Core installation) 6.3.9600.22577
    • Microsoft Windows Server 2016 10.0.14393.8066
    • Microsoft Windows Server 2016 (Server Core installation) 10.0.14393.8066
    • Microsoft Windows Server 2019 10.0.17763.7314
    • Microsoft Windows Server 2019 (Server Core installation) 10.0.17763.7314
    • Microsoft Windows Server 2022 10.0.20348.3692
    • Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.1611
    • Microsoft Windows Server 2025 10.0.26100.4061
    • Microsoft Windows Server 2025 (Server Core installation) 10.0.26100.4061

    Not sure whether and how you are affected? Ask a question about this vulnerability

    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: pwn.watch, CVE.org, Msrc Update Guide

    1.4 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 72.6

    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
    190.13 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 exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
    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
    1.4 %
    Moderate — model estimates 1-10% 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
    72.6
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    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
    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
    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-416

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This is a local privilege escalation with low attack complexity. It needs only low privileges and no user interaction, and it gives full compromise of the host's confidentiality, integrity and availability. Attackers chain it after initial access via phishing, infostealers or stolen VPN/RDP credentials to move from a user context to SYSTEM. From there they dump credentials, tamper with EDR and move laterally, and CLFS has repeatedly been the target of such zero-day chains. CISA currently lists no known ransomware use for this CVE, and the statistical exploitation likelihood is moderate. Confirmed in-the-wild use still outweighs both. Treat it as high priority for multi-user systems (RDS/VDI), admin workstations and any client with mail or web access. Isolated single-purpose servers without interactive users can follow in the regular patch cycle.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Deploy the Microsoft May 2025 security update (Patch Tuesday, 2025-05-13) to all affected Windows clients. Minimum fixed builds: Win10 1507 10.0.10240.21014, 1607 10.0.14393.8066, 1809 10.0.17763.7314, 21H2 10.0.19044.5854, 22H2 10.0.19045.5854, Win11 22H2 10.0.22621.5335, 22H3/23H2 10.0.22631.5335. Look up the exact KB number in the Microsoft Security Update Guide entry for CVE-2025-32701.
      • Patch hosts with many interactive users first: terminal servers, RDS/VDI hosts, Citrix workers and jump hosts. On these, any low-privileged account can escalate straight to SYSTEM.
      • Check servers sharing the same codebase (builds 14393 / 17763) against the vendor advisory. The context lists no server SKUs, so look up the versions there.
      • Verify patch state through your inventory tooling, e.g. Intune, SCCM or MDE TVM. As a fallback, use PowerShell: (Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion').CurrentBuild plus UBR. Log non-compliant systems as risk exceptions with a named owner.
      • Hunt for privilege escalation on endpoints that had initial-access events in the last 30 days (phishing clicks, malware alerts). This bug is normally the second stage of an intrusion chain.
      • Unsupported Windows 10 builds without ESU will not receive the fix. Isolate or replace them.

    2. Runbook step 2

      Mitigation layers

      • Configuration: clfs.sys is a core OS component and cannot be disabled. No vendor workaround is known, so compensating controls must restrict local code execution.
      • Application control: Run WDAC or AppLocker in enforce mode. Block execution from user-writable paths such as %TEMP%, %APPDATA%, C:\Users\Public, C:\ProgramData and Downloads, which is where exploit binaries are typically staged.
      • Endpoint hardening: Enable these ASR rules: "Block executable files unless they meet prevalence, age, or trusted list criteria", "Block process creations originating from PSExec and WMI commands" and "Block credential stealing from LSASS". Also turn on Credential Guard and LSA Protection (RunAsPPL). Together they limit the blast radius after a successful SYSTEM escalation.
      • IAM / least privilege: Restrict interactive logon on servers to the appropriate admin tier. Rotate local admin passwords with Windows LAPS and remove shared local admin accounts, so SYSTEM on one host cannot be turned into lateral movement.
      • Network segmentation: Block client-to-client RDP (TCP 3389), SMB (TCP 445) and WinRM (TCP 5985/5986) via host firewall or network ACLs. An escalated workstation should not become a pivot point.

    3. Runbook step 3

      Detection rules

      • Sysmon EID 11 / MDE DeviceFileEvents: Watch for .blf or container files created outside the usual system paths. KQL: DeviceFileEvents | where FileName endswith ".blf" and not(FolderPath has_any (@"\System32\config", @"\System32\LogFiles", @"\Windows\ServiceProfiles")) | where InitiatingProcessIntegrityLevel in ("Low","Medium")
      • Sysmon EID 1 / Security EID 4688: Flag processes running at IntegrityLevel=System whose parent runs as a standard user and is not a service. Sigma shape: ParentUser != "NT AUTHORITY\SYSTEM" AND User == "NT AUTHORITY\SYSTEM" AND Image endswith ("\cmd.exe","\powershell.exe","\rundll32.exe"). This is the classic token-theft signature.
      • System log / WER: Bugchecks (System EID 1001 BugCheck, EID 41 Kernel-Power) whose minidump references clfs.sys point to failed exploit attempts. Clustered crashes on workstations warrant forensic acquisition.
      • EDR process ancestry: Look for chains like explorer.exe / Office / browser → unknown binary in %TEMP% or C:\Users\Public → SYSTEM shell. These are often followed by lsass.exe access (Sysmon EID 10, GrantedAccess 0x1010/0x1FFFFF).
      • Follow-on activity: New services (System EID 7045) or scheduled tasks (Security EID 4698) created shortly after a suspicious SYSTEM process spawn on the same host indicate post-escalation persistence.

    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

    Use after free in Windows Common Log File System Driver allows an authorized attacker to elevate privileges locally.

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

    Affected products

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

    Affected products
    Affected versionsFixed in
    MicrosoftWindows 10 Version 1507
    • 10.0.10240.0 – < 10.0.10240.21014
    • 10.0.10240.21014
    MicrosoftWindows 10 Version 1607
    • 10.0.14393.0 – < 10.0.14393.8066
    • 10.0.14393.8066
    MicrosoftWindows 10 Version 1809
    • 10.0.17763.0 – < 10.0.17763.7314
    • 10.0.17763.7314
    MicrosoftWindows 10 Version 21H2
    • 10.0.19044.0 – < 10.0.19044.5854
    • 10.0.19044.5854
    MicrosoftWindows 10 Version 22H2
    • 10.0.19045.0 – < 10.0.19045.5854
    • 10.0.19045.5854
    MicrosoftWindows 11 version 22H2
    • 10.0.22621.0 – < 10.0.22621.5335
    • 10.0.22621.5335
    MicrosoftWindows 11 version 22H3
    • 10.0.22631.0 – < 10.0.22631.5335
    • 10.0.22631.5335
    MicrosoftWindows 11 Version 23H2
    • 10.0.22631.0 – < 10.0.22631.5335
    • 10.0.22631.5335
    MicrosoftWindows 11 Version 24H2
    • 10.0.26100.0 – < 10.0.26100.4061
    • 10.0.26100.4061
    MicrosoftWindows Server 2008 R2 Service Pack 1
    • 6.1.7601.0 – < 6.1.7601.27729
    • 6.1.7601.27729
    MicrosoftWindows Server 2008 R2 Service Pack 1 (Server Core installation)
    • 6.1.7601.0 – < 6.1.7601.27729
    • 6.1.7601.27729
    MicrosoftWindows Server 2008 Service Pack 2
    • 6.0.6003.0 – < 6.0.6003.23279
    • 6.0.6003.23279
    MicrosoftWindows Server 2008 Service Pack 2 (Server Core installation)
    • 6.0.6003.0 – < 6.0.6003.23279
    • 6.0.6003.23279
    MicrosoftWindows Server 2012
    • 6.2.9200.0 – < 6.2.9200.25475
    • 6.2.9200.25475
    MicrosoftWindows Server 2012 (Server Core installation)
    • 6.2.9200.0 – < 6.2.9200.25475
    • 6.2.9200.25475
    MicrosoftWindows Server 2012 R2
    • 6.3.9600.0 – < 6.3.9600.22577
    • 6.3.9600.22577
    MicrosoftWindows Server 2012 R2 (Server Core installation)
    • 6.3.9600.0 – < 6.3.9600.22577
    • 6.3.9600.22577
    MicrosoftWindows Server 2016
    • 10.0.14393.0 – < 10.0.14393.8066
    • 10.0.14393.8066
    MicrosoftWindows Server 2016 (Server Core installation)
    • 10.0.14393.0 – < 10.0.14393.8066
    • 10.0.14393.8066
    MicrosoftWindows Server 2019
    • 10.0.17763.0 – < 10.0.17763.7314
    • 10.0.17763.7314
    MicrosoftWindows Server 2019 (Server Core installation)
    • 10.0.17763.0 – < 10.0.17763.7314
    • 10.0.17763.7314
    MicrosoftWindows Server 2022
    • 10.0.20348.0 – < 10.0.20348.3692
    • 10.0.20348.3692
    MicrosoftWindows Server 2022, 23H2 Edition (Server Core installation)
    • 10.0.25398.0 – < 10.0.25398.1611
    • 10.0.25398.1611
    MicrosoftWindows Server 2025
    • 10.0.26100.0 – < 10.0.26100.4061
    • 10.0.26100.4061
    MicrosoftWindows Server 2025 (Server Core installation)
    • 10.0.26100.0 – < 10.0.26100.4061
    • 10.0.26100.4061

    Vendors and products

    Affected operating systems

    Affected operating systems
    Windowsmicrosoftwindows_10_1507—
    Windowsmicrosoftwindows_10_1607—
    Windowsmicrosoftwindows_10_1809—
    Windowsmicrosoftwindows_10_21h2—
    Windowsmicrosoftwindows_10_22h2—
    Windowsmicrosoftwindows_11_22h2—
    Windowsmicrosoftwindows_11_23h2—
    Windowsmicrosoftwindows_11_24h2—
    Windowsmicrosoftwindows_server_2008r2
    Windowsmicrosoftwindows_server_2008—
    Windowsmicrosoftwindows_server_2012r2
    Windowsmicrosoftwindows_server_2012—
    Windowsmicrosoftwindows_server_2016—
    Windowsmicrosoftwindows_server_2019—
    Windowsmicrosoftwindows_server_2022—
    Windowsmicrosoftwindows_server_2022_23h2—
    Windowsmicrosoftwindows_server_2025—

    Weakness classes (CWE)

    • CWE-416Use After Free

      Variant

      The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

      Entry at MITRE CWE-416

    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 CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited

    References & sources

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    Badge preview for CVE-2025-32701
    <a href="https://intel.neosec.eu/en/cve/CVE-2025-32701"><img src="https://intel.neosec.eu/badge/cve/CVE-2025-32701.svg?lang=en" alt="CVE-2025-32701 – NEOSEC Intel" height="20"></a>