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

Is it exploited?

Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 3 Mar 2025, 2,273 days after the CVE record was published.

How likely is exploitation in the next 30 days?

22.2%

EPSS score, percentile 97.7 of all scored records

How severe?

8.4 High

CVSS v3.1 base score, from CISA's enrichment of the record

What should I do?

CISA deadline 24 Mar 2025. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

The CVE record links no vendor advisory, patch or mitigation.

Which versions are affected?

Affected

• 32-bit Systems Service Pack 1
• x64-based Systems Service Pack 1
• (Server Core installation)
• Windows RT 8.1
• 32-bit Systems Service Pack 2
• 32-bit Systems Service Pack 2 (Server Core installation)

and 25 more in the table below

Versions by product

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

What to do

CISA due date for this action: 24 March 2025.

Advisories and patches

The CVE record links no vendor advisory, patch or mitigation.

Linked from CISA's catalog entry

• https://msrc.microsoft.com/update-guide/en-US/advisory/CVE-2018-8639
• https://nvd.nist.gov/vuln/detail/CVE-2018-8639

Affected products and versions

As listed in the CVE record.

And 3 more version entries in the CVE record.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

About this vulnerability

Microsoft Windows Win32k contains an improper resource shutdown or release vulnerability that allows for local, authenticated privilege escalation. An attacker who successfully exploited this vulnerability could run arbitrary code in kernel mode.

Summary: CISA's KEV catalog, as of 28 Oct 2026.

• CISA added CVE-2018-8639 to its Known Exploited Vulnerabilities (KEV) catalog on 3 Mar 2025.
• CISA marks it as known to be used in ransomware campaigns.
• The due date CISA sets for the required action is 24 Mar 2025.
• The CVE record was published on 12 Dec 2018, 2,273 days before it was added to KEV.
• The CVE record carries a CVSS v3.1 base score of 8.4 (High), taken from CISA's enrichment of the record.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 22.2% (percentile 97.7), as of 28 Oct 2026.
• CISA's SSVC assessment in the CVE record: exploitation active, automatable no, technical impact total.

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.

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 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.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

Weakness

• CWE-404: Improper Resource Shutdown or Release

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.

Timeline

References

• 106093 (Vulnerability database)
• portal.msrc.microsoft.com

More exploited Microsoft vulnerabilities

• CVE-2026-96951: Microsoft Windows Command Injection Vulnerability (added 13 Oct 2026)
• CVE-2026-65660: Microsoft SharePoint Code Injection Vulnerability (added 25 Sep 2026)
• CVE-2026-81963: Microsoft Windows Link Following Vulnerability (added 8 Sep 2026)
• CVE-2026-85880: Microsoft Windows Heap-Based Buffer Overflow Vulnerability (added 8 Sep 2026)
• CVE-2019-1068: Microsoft SQL Server Remote Code Execution Vulnerability (added 26 Aug 2026)
• CVE-2026-33824: Microsoft Internet Key Exchange (IKE) Service Extensions Double Free Vulnerability (added 18 Aug 2026)