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

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

• Documented patch — portal.msrc.microsoft.com (NIST National Vulnerability Database)

CISA required action CISA

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

US federal deadline: Mar 24, 2025 — passed 570 day(s) ago

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

1. Identify exposed assets running the affected vendor/product/version combinations (Microsoft Windows 10, Microsoft Windows 10 1507, Microsoft Windows 10 1607…).
2. Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
3. Apply the fixed version or the patch documented under Remediation.
4. EPSS ahead of 98% of scored CVEs: prioritize it in the patch queue.
5. Search available logs for exploit probes matching the vulnerability class (denial of service), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-404 · Improper Resource Shutdown or Release

Other CVEs with this weakness →

CISA KEV details CISA

CISA lists a CVE once it has evidence of exploitation against real targets.

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a reference date.

EPSS over time FIRST

Oct 12, 2026 → Oct 14, 2026 · 3 reading(s) · max 22.18%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

• Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
• Track CPU/memory spikes and availability drops correlated with request patterns.
• Hunt retroactively in logs from before Mar 3, 2025 (KEV listing): exploitation may have started earlier.

Timeline

What happened to this CVE, newest first.

• 2026
• Affected products added · microsoft/windows 7, microsoft/windows server 2012 r2, microsoft/windows rt 8.1, microsoft/windows server 2008, microsof
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• SSVC assessment updated
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• Record published
  Oct 13, 2026
• Fix documented
  Oct 13, 2026 · NIST National Vulnerability Database
• Affected products added · microsoft/windows 10 1507, microsoft/windows 10 1607, microsoft/windows 10 1703, microsoft/windows 10 1709, microsoft/wi
  Oct 13, 2026 · NIST National Vulnerability Database
• CVSS changed · 7.8
  Oct 13, 2026 · NIST National Vulnerability Database
• Source status changed · → Analyzed
  Oct 13, 2026 · NIST National Vulnerability Database
• Added to CISA KEV (detected)
  Oct 13, 2026 · CISA Known Exploited Vulnerabilities
• Record created in this database
  Oct 13, 2026 · CISA Known Exploited Vulnerabilities
• 2025
• Added to CISA KEV catalog
  Mar 2, 2025 · CISA
• 2018
• CVE published
  Dec 11, 2018 · microsoft

Source activity

Repeated readings are counted rather than listed.

• 2× References added · Oct 13, 2026 – Oct 13, 2026
• 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

5 on the record

• portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2018-8639
  Patch, Vendor Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
• www.cisa.gov/known-exploited-vulnerabilities-catalog
  US Government Resource, NIST National Vulnerability Database
• nvd.nist.gov/vuln/detail/CVE-2018-8639
  GitHub Security Advisories
• www.securityfocus.com/bid/106093
  Broken Link, Third Party Advisory, VDB Entry, vdb-entry, x_refsource_BID, NIST National Vulnerability Database
• github.com/advisories/GHSA-93mm-g479-2cx4
  GitHub Security Advisories

Elsewhere on this site

Related CVEs (same products)

• Medium CVE-2026-97844 Role: DNS Server Information Disclosure Vulnerability 2d
• Medium CVE-2026-97839 Role: DNS Server Information Disclosure Vulnerability 2d
• Medium CVE-2026-97840 Role: DNS Server Information Disclosure Vulnerability 2d
• Medium CVE-2026-97841 Role: DNS Server Information Disclosure Vulnerability 2d
• Medium CVE-2026-97842 Role: DNS Server Information Disclosure Vulnerability 2d
• Medium CVE-2026-97843 Role: DNS Server Information Disclosure Vulnerability 2d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

• No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
• No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
• No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2018-8639 is "Microsoft Windows Win32k Improper Resource Shutdown or Release Vulnerability", rated High. It affects Windows 10 (Microsoft); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 7.8 describes technical severity. EPSS 22.18% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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