---
title: "CVE-2018-8639: Microsoft Windows Win32k Improper Resource Shutdown or Release Vulnerability"
url: https://erroneo.us/security/cve/CVE-2018-8639/
description: "CVE-2018-8639 (Microsoft Windows): Exploited in the wild (CISA KEV). An elevation of privilege vulnerability exists in Windows when the Win32k component…"
type: vulnerability-record
section: "Security Digest"
date_published: 2018-12-12
date_modified: 2025-10-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2018-8639"
kev: true
cvss: 8.4
epss: 0.22179
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2018-8639: Microsoft Windows Win32k Improper Resource Shutdown or Release Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run Microsoft Windows. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2025-03-03, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-03-24 ; treat that as the outer limit, not the target. CISA also lists it as known to be used in ransomware campaigns .
- EPSS 22.2% , percentile 98: FIRST’s model estimates a 22.2% chance of exploitation activity in the next 30 days, higher than 98% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Needs local access needed. Lower urgency for most teams unless an attacker could already run code on the machine.

## What it is

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 affects Windows 7, Windows Server 2012 R2, Windows RT 8.1, Windows Server 2008, Windows Server 2019, Windows Server 2012, Windows 8.1, Windows Server 2016, Windows Server 2008 R2, Windows 10, Windows 10 Servers. This CVE ID is unique from CVE-2018-8641.

## Affected products (CVE record)

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

## Severity

- CISA-ADP CVSS 3.1: 8.4 `CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`

## Exploitation

- CISA KEV: added 2025-03-03; federal due date 2025-03-24. Known ransomware use: Known.
- CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- CISA SSVC assessment: exploitation active , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 22.18% probability of exploitation activity in the next 30 days; percentile 98.

## Sources

- [Listed in CISA KEV notes (msrc.microsoft.com)](https://msrc.microsoft.com/update-guide/en-US/advisory/CVE-2018-8639)
- [CVE.org record CVE-2018-8639](https://www.cve.org/CVERecord?id=CVE-2018-8639)
- [NVD entry CVE-2018-8639](https://nvd.nist.gov/vuln/detail/CVE-2018-8639)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2018-8639)
- [106093](http://www.securityfocus.com/bid/106093)
- [portal.msrc.microsoft.com](https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2018-8639)

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Source page: https://erroneo.us/security/cve/CVE-2018-8639/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt