CriticalCVE-2025-29824

    Windows Common Log File System Driver Elevation of Privilege Vulnerability (CVE-2025-29824)

    Published In CISA KEV since Sources: SingCERT, 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. CISA lists it as used in ransomware campaigns. Update Microsoft Windows 10 Version 1507 to version 10.0.10240.20978, Microsoft Windows 10 Version 1607 to version 10.0.14393.7969, Microsoft Windows 10 Version 1809 to version 10.0.17763.7136. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Microsoft Windows 10 Version 1507 lt 10.0.10240.0..10.0.10240.20978
    • Microsoft Windows 10 Version 1607 lt 10.0.14393.0..10.0.14393.7969
    • Microsoft Windows 10 Version 1809 lt 10.0.17763.0..10.0.17763.7136
    • Microsoft Windows 10 Version 21H2 lt 10.0.19044.0..10.0.19044.5737
    • Microsoft Windows 10 Version 22H2 lt 10.0.19045.0..10.0.19045.5737
    • Microsoft Windows 11 version 22H2 lt 10.0.22621.0..10.0.22621.5189
    • Microsoft Windows 11 version 22H3 lt 10.0.22631.0..10.0.22631.5189
    • Microsoft Windows 11 Version 23H2 lt 10.0.22631.0..10.0.22631.5189
    • Microsoft Windows 11 Version 24H2 lt 10.0.26100.0..10.0.26100.3775
    • Microsoft Windows Server 2008 R2 Service Pack 1 lt 6.1.7601.0..6.1.7601.27670
    • Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) lt 6.1.7601.0..6.1.7601.27670
    • Microsoft Windows Server 2008 Service Pack 2 lt 6.0.6003.0..6.0.6003.23220
    • Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) lt 6.0.6003.0..6.0.6003.23220
    • Microsoft Windows Server 2012 lt 6.2.9200.0..6.2.9200.25423
    • Microsoft Windows Server 2012 (Server Core installation) lt 6.2.9200.0..6.2.9200.25423
    • Microsoft Windows Server 2012 R2 lt 6.3.9600.0..6.3.9600.22523
    • Microsoft Windows Server 2012 R2 (Server Core installation) lt 6.3.9600.0..6.3.9600.22523
    • Microsoft Windows Server 2016 lt 10.0.14393.0..10.0.14393.7969
    • Microsoft Windows Server 2016 (Server Core installation) lt 10.0.14393.0..10.0.14393.7969
    • Microsoft Windows Server 2019 lt 10.0.17763.0..10.0.17763.7136
    • Microsoft Windows Server 2019 (Server Core installation) lt 10.0.17763.0..10.0.17763.7136
    • Microsoft Windows Server 2022 lt 10.0.20348.0..10.0.20348.3453
    • Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) lt 10.0.25398.0..10.0.25398.1551
    • Microsoft Windows Server 2025 lt 10.0.26100.0..10.0.26100.3775
    • Microsoft Windows Server 2025 (Server Core installation) lt 10.0.26100.0..10.0.26100.3775
    Fixed in
    • Microsoft Windows 10 Version 1507 10.0.10240.20978
    • Microsoft Windows 10 Version 1607 10.0.14393.7969
    • Microsoft Windows 10 Version 1809 10.0.17763.7136
    • Microsoft Windows 10 Version 21H2 10.0.19044.5737
    • Microsoft Windows 10 Version 22H2 10.0.19045.5737
    • Microsoft Windows 11 version 22H2 10.0.22621.5189
    • Microsoft Windows 11 version 22H3 10.0.22631.5189
    • Microsoft Windows 11 Version 23H2 10.0.22631.5189
    • Microsoft Windows 11 Version 24H2 10.0.26100.3775
    • Microsoft Windows Server 2008 R2 Service Pack 1 6.1.7601.27670
    • Microsoft Windows Server 2008 R2 Service Pack 1 (Server Core installation) 6.1.7601.27670
    • Microsoft Windows Server 2008 Service Pack 2 6.0.6003.23220
    • Microsoft Windows Server 2008 Service Pack 2 (Server Core installation) 6.0.6003.23220
    • Microsoft Windows Server 2012 6.2.9200.25423
    • Microsoft Windows Server 2012 (Server Core installation) 6.2.9200.25423
    • Microsoft Windows Server 2012 R2 6.3.9600.22523
    • Microsoft Windows Server 2012 R2 (Server Core installation) 6.3.9600.22523
    • Microsoft Windows Server 2016 10.0.14393.7969
    • Microsoft Windows Server 2016 (Server Core installation) 10.0.14393.7969
    • Microsoft Windows Server 2019 10.0.17763.7136
    • Microsoft Windows Server 2019 (Server Core installation) 10.0.17763.7136
    • Microsoft Windows Server 2022 10.0.20348.3453
    • Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.1551
    • Microsoft Windows Server 2025 10.0.26100.3775
    • Microsoft Windows Server 2025 (Server Core installation) 10.0.26100.3775

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

    19.3 %

    EPSS score

    Elevated — model estimates 10-50% exploitation likelihood.

    Source: FIRST EPSS, percentile 97.3

    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
    248.30 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), CSA/SingCERT 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
    19.3 %
    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
    97.3
    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
    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
    CISA assessment (SSVC)
    Exploitation: active · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 8 April 2025
    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 CVE sits on KEV because it was burned as a zero-day inside ransomware operations (Microsoft Threat Intelligence attributes observed activity to a Storm cluster deploying RansomEXX-adjacent payloads) as the second stage after initial access — the attacker only needs an ordinary user account to reach SYSTEM. The vector is local, but in real intrusions it is almost always chained with phishing, a browser exploit, or stolen credentials; exploitation likelihood ranks among the highest in the current KEV cohort. Patch-queue placement: ahead of server-only vulnerabilities and on par with active browser zero-days — every unpatched Windows workstation during a live phishing incident is the delta between an EDR alert and domain-wide ransomware.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Deploy the Microsoft April 2025 Patch Tuesday update immediately via WSUS/Intune/SCCM. Target builds per Microsoft advisory: Windows 10 1507 ≥ 10.0.10240.20978, 1607 ≥ 10.0.14393.7969, 1809 ≥ 10.0.17763.7136, 21H2 ≥ 10.0.19044.5737, plus the matching Windows 11 and Server builds. Prioritise terminal servers, jump hosts, developer workstations, VDI golden images.
      • Pull a patch-compliance report for every Windows endpoint (clfs.sys is loaded on all of them) and tag non-compliant hosts on an EDR watchlist until remediated.
      • Review local administrators and any service account with interactive logon rights — the exploit needs local code execution as a normal user, so every reduction in local attack surface (LAPS, no persistent local admin, AppLocker/WDAC) lowers success probability.
      • CISA-KEV ransomware-use flag is set — immediately verify backup integrity, offline copies, and restore times for critical file servers and domain controllers; harden RBAC on backup consoles against privilege escalation.
      • Raise an out-of-band emergency change and document the deployment for NIS2 evidentiary purposes.

    2. Runbook step 2

      Mitigation layers

      • Endpoint hardening: enable the ASR rule "Block abuse of exploited vulnerable signed drivers", keep Microsoft's Vulnerable Driver Blocklist current, and enforce HVCI/Memory Integrity — materially raises the bar for kernel UAF exploitation.
      • Least privilege: forbid standard users from executing arbitrary binaries out of %TEMP%, %APPDATA% or Downloads via an AppLocker/WDAC publisher allowlist; CLFS exploitation is typically delivered as a post-phishing EoP stage.
      • Network segmentation: block workstation-to-workstation SMB (TCP 445) and RPC (TCP 135 plus dynamic ports) via host firewall or microsegmentation to slow lateral movement after a successful privilege escalation.
      • Switch EDR from "audit" to "block" for credential-access and kernel-driver-load telemetry; enforce tamper protection so a SYSTEM-level process cannot disable the agent.
      • Harden upstream delivery vectors: block Office macros from the internet, enforce SmartScreen and MOTW — reduces the paths through which CLFS EoP is typically reached.
      • For legacy systems that cannot be patched (ESU expired, appliance Windows): isolate into a dedicated VLAN, access only via jump host, no internet egress.

    3. Runbook step 3

      Detection rules

      • Sysmon EID 11 (FileCreate) and 23 (FileDelete) for suspicious .blf/.bls files outside the usual CLFS paths (%SystemRoot%\System32\config, %ProgramData%); public PoCs drop crafted Base Log Files into user-writable directories.
      • Sysmon EID 1 where ParentImage lives under %TEMP%\ or %AppData%\Local\Temp\ or is an unsigned binary that shortly after spawns a SYSTEM-integrity child — classic EoP signature. KQL shape: DeviceProcessEvents | where InitiatingProcessIntegrityLevel == "Medium" and ProcessIntegrityLevel == "System" | where TimeGenerated > ago(1h).
      • Windows Event ID 4672 (special privileges assigned) for accounts that normally never hold SYSTEM, correlated with preceding 4688 events from a low-integrity process.
      • EDR telemetry on unexpected loads/writes against clfs.sys or on CLFS API calls (CreateLogFile, AddLogContainer) from non-system processes; Microsoft reported the PipeMagic backdoor as a companion payload — hunt for named-pipe pattern \.\pipe\1.<hex> as an IOC.
      • Sigma shape: process_creation with Image|endswith: '\dllhost.exe' and a command line lacking the usual CLSID argument — observed campaigns used dllhost.exe to masquerade the exploit host process.

    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: CSA/SingCERT, pwn.watch, NVD (NIST), Microsoft Security Update Guide, CISA KEV Catalog, cvelistv5, 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 – < 10.0.10240.20978
    • 10.0.10240.20978
    MicrosoftWindows 10 Version 1607
    • 10.0.14393.0 – < 10.0.14393.7969
    • 10.0.14393.7969
    MicrosoftWindows 10 Version 1809
    • 10.0.17763.0 – < 10.0.17763.7136
    • 10.0.17763.7136
    MicrosoftWindows 10 Version 21H2
    • 10.0.19044.0 – < 10.0.19044.5737
    • 10.0.19044.5737
    MicrosoftWindows 10 Version 22H2
    • 10.0.19045.0 – < 10.0.19045.5737
    • 10.0.19045.5737
    MicrosoftWindows 11 version 22H2
    • 10.0.22621.0 – < 10.0.22621.5189
    • 10.0.22621.5189
    MicrosoftWindows 11 version 22H3
    • 10.0.22631.0 – < 10.0.22631.5189
    • 10.0.22631.5189
    MicrosoftWindows 11 Version 23H2
    • 10.0.22631.0 – < 10.0.22631.5189
    • 10.0.22631.5189
    MicrosoftWindows 11 Version 24H2
    • 10.0.26100.0 – < 10.0.26100.3775
    • 10.0.26100.3775
    MicrosoftWindows Server 2008 R2 Service Pack 1
    • 6.1.7601.0 – < 6.1.7601.27670
    • 6.1.7601.27670
    MicrosoftWindows Server 2008 R2 Service Pack 1 (Server Core installation)
    • 6.1.7601.0 – < 6.1.7601.27670
    • 6.1.7601.27670
    MicrosoftWindows Server 2008 Service Pack 2
    • 6.0.6003.0 – < 6.0.6003.23220
    • 6.0.6003.23220
    MicrosoftWindows Server 2008 Service Pack 2 (Server Core installation)
    • 6.0.6003.0 – < 6.0.6003.23220
    • 6.0.6003.23220
    MicrosoftWindows Server 2012
    • 6.2.9200.0 – < 6.2.9200.25423
    • 6.2.9200.25423
    MicrosoftWindows Server 2012 (Server Core installation)
    • 6.2.9200.0 – < 6.2.9200.25423
    • 6.2.9200.25423
    MicrosoftWindows Server 2012 R2
    • 6.3.9600.0 – < 6.3.9600.22523
    • 6.3.9600.22523
    MicrosoftWindows Server 2012 R2 (Server Core installation)
    • 6.3.9600.0 – < 6.3.9600.22523
    • 6.3.9600.22523
    MicrosoftWindows Server 2016
    • 10.0.14393.0 – < 10.0.14393.7969
    • 10.0.14393.7969
    MicrosoftWindows Server 2016 (Server Core installation)
    • 10.0.14393.0 – < 10.0.14393.7969
    • 10.0.14393.7969
    MicrosoftWindows Server 2019
    • 10.0.17763.0 – < 10.0.17763.7136
    • 10.0.17763.7136
    MicrosoftWindows Server 2019 (Server Core installation)
    • 10.0.17763.0 – < 10.0.17763.7136
    • 10.0.17763.7136
    MicrosoftWindows Server 2022
    • 10.0.20348.0 – < 10.0.20348.3453
    • 10.0.20348.3453
    MicrosoftWindows Server 2022, 23H2 Edition (Server Core installation)
    • 10.0.25398.0 – < 10.0.25398.1551
    • 10.0.25398.1551
    MicrosoftWindows Server 2025
    • 10.0.26100.0 – < 10.0.26100.3775
    • 10.0.26100.3775
    MicrosoftWindows Server 2025 (Server Core installation)
    • 10.0.26100.0 – < 10.0.26100.3775
    • 10.0.26100.3775

    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
    CSA/SingCERTZero-Day Vulnerability in Microsoft Windows Common Log File System (CLFS) Driver (opens in a new tab)CSA/SingCERTactively exploited

    References & sources

    • Microsoft Security Update GuideWindows Common Log File System Driver Elevation of Privilege VulnerabilityVendor advisory, Patch, Vendor advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2025-29824government-resource, US government resource
    • vicarius.iovsociety/posts/cve-2025-29824-windows-common-log-file-system-dr…Exploit, Third-party advisory
    • vicarius.iovsociety/posts/cve-2025-29824-windows-common-log-file-system-dr…Exploit, Third-party advisory
    • pwn.watchpwn.watch: Microsoft Windows: Windows Common Log File System (CLFS) Driver Use-After-Free Vulnerabilitypwn-watch
    • Microsoft Security Update GuideMicrosoft advisory: Microsoft Windowspwn-watch
    • NVD (NIST)NVD: CVE-2025-29824pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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    Badge preview for CVE-2025-29824
    <a href="https://intel.neosec.eu/en/cve/CVE-2025-29824"><img src="https://intel.neosec.eu/badge/cve/CVE-2025-29824.svg?lang=en" alt="CVE-2025-29824 – NEOSEC Intel" height="20"></a>