Microsoft Windows Win32k Improper Resource Shutdown or Release Vulnerability
Microsoft / Windows
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.
- CVE identifier
- CVE-2018-8639
- Added to KEV
- Mar 3, 2025
- CISA catalog dueDate
- Mar 24, 2025
The dates above are catalog fields. The addition date does not establish when the vulnerability was discovered or first exploited. Confirm which requirements apply to your organisation separately.
Publisher's 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.
This wording is attributed to the CISA snapshot. Verify current vendor guidance, affected versions and your deployment before applying changes.
Keep the signals separate.
- Ransomware use, as reported by CISA
- Known
- CVSS severity
- Not supplied by KEV
- EPSS probability
- 22.18%
EPSS score date: 2026-09-27T12:00:21Z. Percentile: 97.60%. Model version: v2026.06.15.
A dated estimate of exploitation probability over the following 30 days, not a severity score or a probability of a breach in your environment.
Inspect the EPSS source ↗“Unknown” ransomware use is an unknown source field, not proof that ransomware activity has not occurred.
Source notes
https://msrc.microsoft.com/update-guide/en-US/advisory/CVE-2018-8639 ; https://nvd.nist.gov/vuln/detail/CVE-2018-8639
Source & freshness
Source updated: Sep 27, 2026, 9:30 PM UTC
Successfully checked: Sep 27, 2026, 11:50 PM UTC
This snapshot is older than 36 hours. Check current publisher guidance.
Automated source record, not an editorial advisory or an independent discovery. No affected or fixed version is inferred, and no organisation-specific risk rating is generated.