CriticalCVE-2019-1458

    Microsoft Win32k Privilege Escalation Vulnerability (CVE-2019-1458)

    Published In CISA KEV since Sources: CVE.org

    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'.

    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 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 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 Server eq 2016..2016
    • Microsoft Windows Server eq 2016 (Core installation)..2016 (Core installation)
    • 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 32-bit Systems Service Pack 2 (Core installation)..2008 for 32-bit Systems Service Pack 2 (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 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)
    • 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 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 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)

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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

    74.4 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.49

    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
    243.19 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
    74.4 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    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
    99.49
    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 4 January 2022

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This is a local privilege escalation that needs only low privileges and no user interaction. It was used early on alongside a browser exploit to escape the sandbox, and public exploit code has been available for years. CISA flags it as used in ransomware campaigns, where it typically serves as the second stage after phishing or a compromised remote-access foothold, giving attackers SYSTEM rights, then credential access and lateral movement. Exploitation likelihood is very high. Exposure concentrates in estates with legacy Windows (Windows 7/Server 2008, early Windows 10 builds), which are common in KRITIS, manufacturing and OT-adjacent networks. Fully patched hosts carry little residual risk. Any unpatched, interactively used host should be treated as critical and patched, migrated or isolated first.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Verify and enforce patch compliance: Microsoft fixed this vulnerability in the December 2019 security update (Patch Tuesday). Every later cumulative update or Monthly Rollup includes the fix. Look up the OS-specific KB numbers in the MSRC advisory for CVE-2019-1458. Use WSUS/SCCM/Intune to find hosts with no patch level from December 2019 or later.
      • Inventory legacy systems: Windows 7, Windows 8.1/RT 8.1, Server 2008 and Windows 10 1507/1607 are largely end-of-life. Check whether ESU updates are applied. Treat any host with no patches at all as at risk of compromise.
      • Patch interactive hosts first: Prioritise RDS/terminal servers, Citrix workers, jump hosts and clients used for browsing and email. These are where attackers typically gain local code execution after initial access.
      • Isolate suspect hosts: Use EDR network containment immediately on unpatched hosts that show privilege-escalation, credential-dumping or pre-ransomware alerts. Then rotate local admin and service-account passwords, because SYSTEM-level access implies LSASS exposure.
      • Lock down unpatchable systems: Hosts without ESU coverage that cannot be migrated soon should lose interactive logon for standard users and move to an isolated segment.

    2. Runbook step 2

      Mitigation layers

      • No vendor workaround: The advisory provides no configuration workaround. Compensating controls therefore focus on blocking the local code execution that must come first.
      • Application control (endpoint hardening): Use WDAC or AppLocker to deny execution from user-writable paths (%APPDATA%, %TEMP%, %USERPROFILE%\Downloads). Also enable ASR rules such as "Block executable files unless they meet prevalence, age or trusted list criterion" and "Block Office applications from creating child processes".
      • Close initial-access vectors: Keep browsers (Chrome/Edge) strictly current, because this flaw has been chained with browser exploits to escape the sandbox. Block macros from internet-sourced files via GPO.
      • IAM/least privilege: Remove local admin rights and deploy LAPS for local admin accounts. Enable Credential Guard and LSA protection (RunAsPPL) to limit what an attacker can do with SYSTEM access (credential theft, lateral movement).
      • Network segmentation: Put EOL systems in a dedicated VLAN and allow egress only to defined destinations. Block SMB (445/tcp), RDP (3389/tcp) and WinRM (5985/5986 tcp) from that segment towards server and domain-controller networks.
      • Public exploit code: A Metasploit module exists for this vulnerability. Run the EDR exploit-protection policy in block mode on affected hosts.

    3. Runbook step 3

      Detection rules

      • Integrity jump in the process chain (EDR/MDE): Look for a child process running as SYSTEM whose parent runs in user context. KQL: DeviceProcessEvents | where ProcessIntegrityLevel == "System" and InitiatingProcessIntegrityLevel in ("Medium","Low") and InitiatingProcessAccountSid != "S-1-5-18"
      • Sysmon EID 1 / Security 4688: Look for cmd.exe, powershell.exe or rundll32.exe with User = NT AUTHORITY\SYSTEM and IntegrityLevel = System whose ParentImage is a browser, an Office process or a binary under \AppData\ or \Temp\. Sigma shape: selection: IntegrityLevel: System, ParentImage|contains: ['\AppData\','\Temp\','\chrome.exe','\iexplore.exe'].
      • Post-escalation activity: Watch for Sysmon EID 10 targeting lsass.exe (GrantedAccess 0x1010/0x1410), Security 4672 for unexpected accounts, and 7045 or 4697 (new service) shortly after an integrity jump. Correlate these events within a 5-minute window.
      • Pre-ransomware behaviour: Flag vssadmin delete shadows, wbadmin delete catalog or bcdedit /set recoveryenabled no on hosts that lack the December 2019 patch level. SPL: index=wineventlog EventCode=4688 (New_Process_Name="*vssadmin.exe" CommandLine="*delete shadows*")
      • win32k crashes: Bugchecks (System log, Event ID 1001 / BugCheck) referencing win32k.sys or win32kfull.sys on unpatched hosts may indicate failed exploitation attempts.

    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'.

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

    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
    • RT 8.1
    • 10 for 32-bit Systems
    • 8.1 for 32-bit systems
    • 10 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
    • 8.1 for x64-based systems
    • —
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    MicrosoftWindows Server
    • 2008 for Itanium-Based Systems Service Pack 2
    • 2012 R2
    • 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)
    • 2008 R2 for x64-based Systems Service Pack 1 (Core installation)
    • 2016 (Core installation)
    • 2016
    • 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_7—
    Windowsmicrosoftwindows_8.1—
    Windowsmicrosoftwindows_rt_8.1—
    Windowsmicrosoftwindows_server_2008r2
    Windowsmicrosoftwindows_server_2008—
    Windowsmicrosoftwindows_server_2012r2
    Windowsmicrosoftwindows_server_2012—
    Windowsmicrosoftwindows_server_2016—

    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
    Packet StormMicrosoft Windows WizardOpium Local Privilege Escalation (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—
    Packet StormMicrosoft Windows Uninitialized Variable Local Privilege Escalation (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—

    References & sources

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