CriticalCVE-2019-0859

    Microsoft Win32k Privilege Escalation Vulnerability (CVE-2019-0859)

    Published In CISA KEV since Sources: CVE.org

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    What is affected, what to do

    An elevation of privilege vulnerability exists in Windows when the Win32k component fails to properly handle objects in memory, aka 'Win32k Elevation of Privilege Vulnerability'. This CVE ID is unique from CVE-2019-0685, CVE-2019-0803.

    The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Microsoft Windows eq 7 for 32-bit Systems Service Pack 1..7 for 32-bit Systems Service Pack 1
    • Microsoft Windows eq 7 for x64-based Systems Service Pack 1..7 for x64-based Systems Service Pack 1
    • Microsoft Windows eq 8.1 for 32-bit systems..8.1 for 32-bit systems
    • Microsoft Windows eq 8.1 for x64-based systems..8.1 for x64-based systems
    • Microsoft Windows eq RT 8.1..RT 8.1
    • Microsoft Windows eq 10 for 32-bit Systems..10 for 32-bit Systems
    • Microsoft Windows eq 10 for x64-based Systems..10 for x64-based Systems
    • Microsoft Windows eq 10 Version 1607 for 32-bit Systems..10 Version 1607 for 32-bit Systems
    • Microsoft Windows eq 10 Version 1607 for x64-based Systems..10 Version 1607 for x64-based Systems
    • Microsoft Windows eq 10 Version 1703 for 32-bit Systems..10 Version 1703 for 32-bit Systems
    • Microsoft Windows eq 10 Version 1703 for x64-based Systems..10 Version 1703 for x64-based Systems
    • Microsoft Windows eq 10 Version 1709 for 32-bit Systems..10 Version 1709 for 32-bit Systems
    • Microsoft Windows eq 10 Version 1709 for x64-based Systems..10 Version 1709 for x64-based Systems
    • Microsoft Windows eq 10 Version 1803 for 32-bit Systems..10 Version 1803 for 32-bit Systems
    • Microsoft Windows eq 10 Version 1803 for x64-based Systems..10 Version 1803 for x64-based Systems
    • Microsoft Windows eq 10 Version 1803 for ARM64-based Systems..10 Version 1803 for ARM64-based Systems
    • Microsoft Windows eq 10 Version 1809 for 32-bit Systems..10 Version 1809 for 32-bit Systems
    • Microsoft Windows eq 10 Version 1809 for x64-based Systems..10 Version 1809 for x64-based Systems
    • Microsoft Windows eq 10 Version 1809 for ARM64-based Systems..10 Version 1809 for ARM64-based Systems
    • Microsoft Windows eq 10 Version 1709 for ARM64-based Systems..10 Version 1709 for ARM64-based Systems
    • Microsoft Windows Server eq 2008 R2 for x64-based Systems Service Pack 1 (Core installation)..2008 R2 for x64-based Systems Service Pack 1 (Core installation)
    • Microsoft Windows Server eq 2008 R2 for Itanium-Based Systems Service Pack 1..2008 R2 for Itanium-Based Systems Service Pack 1
    • Microsoft Windows Server eq 2008 R2 for x64-based Systems Service Pack 1..2008 R2 for x64-based Systems Service Pack 1
    • Microsoft Windows Server eq 2008 for 32-bit Systems Service Pack 2 (Core installation)..2008 for 32-bit Systems Service Pack 2 (Core installation)
    • Microsoft Windows Server eq 2012..2012
    • Microsoft Windows Server eq 2012 (Core installation)..2012 (Core installation)
    • Microsoft Windows Server eq 2012 R2..2012 R2
    • Microsoft Windows Server eq 2012 R2 (Core installation)..2012 R2 (Core installation)
    • Microsoft Windows Server eq 2016..2016
    • Microsoft Windows Server eq 2016 (Core installation)..2016 (Core installation)
    • Microsoft Windows Server eq version 1709 (Core Installation)..version 1709 (Core Installation)
    • Microsoft Windows Server eq version 1803 (Core Installation)..version 1803 (Core Installation)
    • Microsoft Windows Server eq 2019..2019
    • Microsoft Windows Server eq 2019 (Core installation)..2019 (Core installation)
    • Microsoft Windows Server eq 2008 for Itanium-Based Systems Service Pack 2..2008 for Itanium-Based Systems Service Pack 2
    • Microsoft Windows Server eq 2008 for 32-bit Systems Service Pack 2..2008 for 32-bit Systems Service Pack 2
    • Microsoft Windows Server eq 2008 for x64-based Systems Service Pack 2..2008 for x64-based Systems Service Pack 2
    • Microsoft Windows Server eq 2008 for x64-based Systems Service Pack 2 (Core installation)..2008 for x64-based Systems Service Pack 2 (Core installation)

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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

    4.2 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 91.0

    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
    230.19 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
    4.2 %
    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
    91.0
    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 7 February 2025

    Response and mitigation

    Why act now?

    Prioritisation rationale

    The flaw requires local access with low privileges but no user interaction, and it yields full kernel-level control. That makes it a classic second link in an attack chain: after phishing or webshell access, it lifts the attacker to SYSTEM. CISA flags known ransomware use, and its exploitation likelihood sits well above the average CVE. Treat it as high priority for organisations with large, heterogeneous client fleets, legacy builds or shared terminal servers. On fully patched, current Windows builds the residual risk is low, and the effort shifts to hunting down uninventoried legacy machines.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Deploy the Microsoft security update for CVE-2019-0859 to all affected Windows clients and servers. The fix ships in Microsoft's cumulative updates. Look up the KB number per build in the MSRC advisory. Any later cumulative update also closes the flaw.
      • Inventory patch state via WSUS, Intune, SCCM or Defender Vulnerability Management (DeviceTvmSoftwareVulnerabilities | where CveId == "CVE-2019-0859"). Flag every host missing the relevant cumulative update as vulnerable.
      • Identify hosts still on Windows 10 1507, 1607, 1703 or 1709. These builds are largely out of support. Migrate them to a supported release or move them into an isolated segment until that is done.
      • Prioritise hosts with a known initial-access event (phishing payload, webshell, malicious macro). This is a local privilege escalation to SYSTEM, so an already compromised user context is the critical precondition.
      • On suspected exploitation, isolate the host via EDR and capture memory and triage data. Then rotate every credential cached on the host, especially domain and service accounts. After a kernel compromise, treat LSASS as fully exposed.

    2. Runbook step 2

      Mitigation layers

      • Endpoint hardening / application control: Run WDAC or AppLocker in enforce mode. Block execution from %TEMP%, %APPDATA%, %LOCALAPPDATA% and C:\Users\Public, where exploit binaries are typically dropped.
      • PowerShell restrictions: Enforce Constrained Language Mode, enable Script Block Logging (EID 4104) and remove PowerShell v2. This makes staged exploit delivery harder.
      • Exploit Protection: Evaluate the per-process "Disable Win32k system calls" mitigation for applications that do not need GUI syscalls. Also enable the ASR rules covering Office child processes and executable content from email.
      • IAM / least privilege: Remove local admin rights, use LAPS for local admin accounts and enforce admin tiering (Tier 0/1/2). A workstation escalated to SYSTEM should not hold cached domain-admin credentials.
      • Credential Guard / LSA protection: Enable RunAsPPL and Credential Guard. This limits post-escalation credential dumping, although a kernel exploit can in principle defeat these controls.
      • Network segmentation: Block SMB (445), RDP (3389) and WinRM (5985/5986) between client VLANs. This blunts the lateral movement that ransomware operators typically perform after escalating.

    3. Runbook step 3

      Detection rules

      • Integrity-level jump (EDR/Defender): DeviceProcessEvents | where ProcessIntegrityLevel == "System" and InitiatingProcessIntegrityLevel in ("Low","Medium") and InitiatingProcessAccountName !endswith "$". Look for SYSTEM processes whose parent ran unprivileged.
      • Sysmon EID 1 / Security EID 4688: Flag cmd.exe, powershell.exe or rundll32.exe running as NT AUTHORITY\SYSTEM when the parent is a user process (explorer.exe, Office, a browser) rather than services.exe. Sigma shape: ParentUser != SYSTEM AND User == SYSTEM AND ParentImage NOT IN (services.exe, svchost.exe).
      • Unknown binaries in user paths: Correlate Sysmon EID 1 and EID 11 for unsigned EXE/DLL files in \AppData\ or \Temp\ that spawn a SYSTEM child within seconds. Check the hashes against threat intel.
      • Post-escalation follow-on: Watch for Sysmon EID 10 access to lsass.exe (GrantedAccess 0x1010/0x1FFFFF). Other indicators are EID 4672 for unusual accounts, EID 7045 or 4697 (new service) and shadow copy deletion (vssadmin delete shadows). The last one is a classic ransomware precursor.
      • Crash telemetry: Hunt for Event ID 1001 (BugCheck) or WER reports referencing win32k*.sys on unpatched hosts. Failed exploit attempts frequently cause blue screens.

    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

    An elevation of privilege vulnerability exists in Windows when the Win32k component fails to properly handle objects in memory, aka 'Win32k Elevation of Privilege Vulnerability'. This CVE ID is unique from CVE-2019-0685, CVE-2019-0803.

    Source: CISA KEV Catalog, NVD (NIST), cvelistv5

    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 1803 for x64-based Systems
    • 10 Version 1709 for ARM64-based Systems
    • RT 8.1
    • 10 Version 1809 for ARM64-based Systems
    • 10 Version 1709 for x64-based Systems
    • 10 Version 1703 for 32-bit Systems
    • 10 for 32-bit Systems
    • 10 for x64-based Systems
    • 8.1 for 32-bit systems
    • 10 Version 1803 for 32-bit Systems
    • 10 Version 1703 for x64-based Systems
    • 10 Version 1607 for 32-bit Systems
    • 7 for x64-based Systems Service Pack 1
    • 10 Version 1607 for x64-based Systems
    • 7 for 32-bit Systems Service Pack 1
    • 10 Version 1809 for x64-based Systems
    • 10 Version 1809 for 32-bit Systems
    • 8.1 for x64-based systems
    • 10 Version 1709 for 32-bit Systems
    • 10 Version 1803 for ARM64-based Systems
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    MicrosoftWindows Server
    • 2008 for Itanium-Based Systems Service Pack 2
    • 2012 R2
    • 2019
    • version 1709 (Core Installation)
    • 2008 for x64-based Systems Service Pack 2 (Core installation)
    • 2008 R2 for x64-based Systems Service Pack 1
    • 2012 (Core installation)
    • 2008 for 32-bit Systems Service Pack 2 (Core installation)
    • 2008 for 32-bit Systems Service Pack 2
    • 2008 R2 for Itanium-Based Systems Service Pack 1
    • 2012
    • 2012 R2 (Core installation)
    • 2019 (Core installation)
    • 2008 R2 for x64-based Systems Service Pack 1 (Core installation)
    • 2016 (Core installation)
    • 2016
    • version 1803 (Core Installation)
    • 2008 for x64-based Systems Service Pack 2
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    Vendors and products

    Affected operating systems

    Affected operating systems
    Windowsmicrosoftwindows_10_1507—
    Windowsmicrosoftwindows_10_1607—
    Windowsmicrosoftwindows_10_1703—
    Windowsmicrosoftwindows_10_1709—
    Windowsmicrosoftwindows_10_1803—
    Windowsmicrosoftwindows_10_1809—
    Windowsmicrosoftwindows_7—
    Windowsmicrosoftwindows_8.1—
    Windowsmicrosoftwindows_rt_8.1—
    Windowsmicrosoftwindows_server_1709—
    Windowsmicrosoftwindows_server_1803—
    Windowsmicrosoftwindows_server_2008r2
    Windowsmicrosoftwindows_server_2008—
    Windowsmicrosoftwindows_server_2012r2
    Windowsmicrosoftwindows_server_2012—
    Windowsmicrosoftwindows_server_2016—
    Windowsmicrosoftwindows_server_2019—

    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

    • portal.msrc.microsoft.comen-US/security-guidance/advisory/CVE-2019-0859x_refsource_MISC
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2019-0859government-resource
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