Microsoft Win32k Privilege Escalation Vulnerability (CVE-2019-0803)
Published In CISA KEV since Sources: Schneider Electric, 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'. This CVE ID is unique from CVE-2019-0685, CVE-2019-0859.
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)
- Microsoft Windows
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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: Schneider Electric, CVE.org
45.2 %
EPSS score
Elevated — model estimates 10-50% exploitation likelihood.
Source: FIRST EPSS, percentile 98.8
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- 242.06 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- 45.2 %
- 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- 98.8
- 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
Response and mitigation
Why act now?
Prioritisation rationale
This CVE is on KEV because it has been observed in ransomware campaigns as the privilege-escalation step after an initial-access dropper (typically phishing or drive-by), lifting the attacker from Medium IL to SYSTEM so they can disable AV, delete shadow copies and move laterally. The CVSS vector is local and needs an authenticated session, but Win32k EoPs are a standard building block in nearly every end-to-end Windows attack chain, and exploitation likelihood sits well above the field average. Any remaining Windows 7, 8.1, Server 2008 R2, Server 2012 or early Windows 10 build (RTM through 1809) must be treated as critical; current Windows 10/11 builds are not affected. For NIS2-regulated organisations this is a "patch-this-week" item, especially on OT jump hosts, terminal servers and VDI pools with shared user sessions where a single compromised account becomes a stepping stone for the whole estate.
Runbook step 1
Immediate response (0-24 h)
- Deploy the Microsoft April 2019 Patch Tuesday fix referenced in MSRC advisory for CVE-2019-0803: push the Security-Only or Monthly Rollup to Windows 7 SP1, Server 2008 R2, Windows 8.1/RT, Server 2012/R2 and Windows 10 builds (RTM, 1607, 1703, 1709, 1803, 1809) plus matching server editions, prioritising endpoints and multi-user hosts.
- Identify legacy systems without ESU coverage (Windows 7 outside Extended Security Updates, Server 2008 R2 beyond ESU) — no patch is available for those; isolate them into a quarantined VLAN or accelerate migration.
- Remove local admin rights from standard users and roll out LAPS: the exploit requires a local authenticated session, so denying standing admin rights blunts the post-EoP blast radius.
- Switch EDR policy to Block for kernel-exploit techniques (token stealing, user-process spawning SYSTEM children); enable Microsoft Defender Exploit Guard and ASR rules "Block credential stealing from LSASS" and "Block Office child processes" if still in audit mode.
- Retrospective hunt over the last 14 days for stage-1 droppers (phishing payloads, drive-by downloads, malicious macros), since Win32k EoPs are almost always stage-2 after an initial access technique.
Runbook step 2
Mitigation layers
- Network segmentation: move unpatchable legacy hosts into a dedicated VLAN with no east-west reachability to file servers, DCs or jump hosts; access only via session broker or PAW.
- Application control: enforce WDAC or AppLocker on user-writeable paths (%AppData%, %Temp%, Downloads) to stop downloaded EoP loaders from executing in the first place.
- Credential hygiene: enforce a tiered-admin model, block domain-admin logons on workstations (Restricted Admin, Protected Users group, Authentication Policies) so a kernel EoP does not open a direct path to Tier-0 credentials.
- Attack surface reduction: enable HVCI/Memory Integrity and Credential Guard where hardware supports it — significantly raises the bar for kernel-mode code execution and token tampering even on unpatched Win32k.
- Harden the delivery vector: ASR rules, Protected View, macro blocking from the Internet, and running Edge/Chrome in a restricted app container to shrink the preceding dropper surface.
- Monitoring baseline: deploy Sysmon with a vetted config (SwiftOnSecurity or Olaf Hartong) on all endpoints, at minimum EIDs 1, 8, 10, 11, 25.
Runbook step 3
Detection rules
- Sysmon EID 10 (ProcessAccess) with GrantedAccess 0x1410/0x1010 against lsass.exe or the System PID from a non-SYSTEM process — the classic token-stealing fingerprint following a kernel EoP.
- Windows Security EID 4688 / Sysmon EID 1 process-ancestry anomaly where a user-context process (Office, browser, script host) spawns a child running as NT AUTHORITY\SYSTEM; KQL sketch:
DeviceProcessEvents | where InitiatingProcessAccountName != "SYSTEM" and AccountName == "SYSTEM" and InitiatingProcessParentFileName in ("winword.exe","excel.exe","outlook.exe","chrome.exe","msedge.exe"). - Sigma shape for integrity-level jump:
selection: EventID: 4688, NewProcessName endswith cmd.exe|powershell.exe, TokenElevationType: "%%1936"from a process whose parent was running at Medium IL. - Windows System log EID 41/1001 (Bugcheck/WER) with faulting module win32kfull.sys or win32k.sys clustering on a single host — failed exploit attempts frequently crash the kernel.
- EDR telemetry on suspicious NtUserMessageCall/SetWindowLongPtr callback manipulation; if the EDR exposes SSDT or kernel-callback registrations, alert on unprivileged processes attempting to register them.
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-2019-0859.
Source: schneider_csaf, cvelistv5, CISA KEV Catalog, NVD (NIST)
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Microsoft | Windows |
|
|
| Microsoft | Windows Server |
|
|
| Schneider Electric | Microsoft Windows |
|
|
Vendors and products
- Microsoft Microsoft Windows
- Microsoft Windows 10 1507
- Microsoft Microsoft Windows 10 1607
- Microsoft Windows 10 1703
- Microsoft Windows 10 1709
- Microsoft Windows 10 1803
- Microsoft Microsoft Windows 10 1809
- Microsoft Microsoft Windows 7
- Microsoft Microsoft Windows 8.1
- Microsoft Microsoft Windows RT 8.1
- Microsoft Windows Server
- Microsoft Windows Server 1709
Affected operating systems
| Family | Vendor | Product | Version |
|---|---|---|---|
| Windows | microsoft | windows_10_1507 | — |
| Windows | microsoft | windows_10_1607 | — |
| Windows | microsoft | windows_10_1703 | — |
| Windows | microsoft | windows_10_1709 | — |
| Windows | microsoft | windows_10_1803 | — |
| Windows | microsoft | windows_10_1809 | — |
| Windows | microsoft | windows_7 | — |
| Windows | microsoft | windows_8.1 | — |
| Windows | microsoft | windows_rt_8.1 | — |
| Windows | microsoft | windows_server_1709 | — |
| Windows | microsoft | windows_server_1803 | — |
| 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 | — |
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.
| Source | Reference | Maturity | Published |
|---|---|---|---|
| CISA KEV Catalog | CISA Known Exploited Vulnerability (opens in a new tab)cisa.gov | actively exploited | |
| Packet Storm | Microsoft Windows Win32k Privilege Escalation (opens in a new tab)packetstormsecurity.com | PoC (publicly reported)reported, not verified | — |
References & sources
- portal.msrc.microsoft.comen-US/security-guidance/advisory/CVE-2019-0803x_refsource_MISC
- packetstormsecurity.comfiles/153034/Microsoft-Windows-Win32k-Privilege-Escalation.htmlx_refsource_MISC
- cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2019-0803government-resource
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<a href="https://intel.neosec.eu/en/cve/CVE-2019-0803"><img src="https://intel.neosec.eu/badge/cve/CVE-2019-0803.svg?lang=en" alt="CVE-2019-0803 – NEOSEC Intel" height="20"></a>