CVE-2026-40369: Heap-based buffer overflow in Windows Kernel allows an authorized attacker to elevate privileges locally.

Q: How do I fix CVE-2026-40369?

windows 11 24h2: upgrade to 10.0.26100.8390; windows 11 25h2: upgrade to 10.0.26200.8390; windows 11 26h1: upgrade to 10.0.28000.2113. Exact commands for each OS are on this page.

Q: Is CVE-2026-40369 being exploited?

CVE-2026-40369 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-40369 affect?

CVE-2026-40369 affects windows 11 24h2, windows 11 25h2, windows 11 26h1. Severity is high (CVSS 7.8). Heap-based buffer overflow in Windows Kernel allows an authorized attacker to elevate privileges locally.

Q: How urgent is CVE-2026-40369?

Priority 60/100. High severity; EPSS top 8%: very likely to be exploited; Public exploit reference; On your watchlist

This week

HIGH 7.8WATCHLISTUPGRADEUPGRADEUPGRADE

CVE-2026-40369 is a high-severity flaw (CVSS 7.8) affecting windows 11 24h2, windows 11 25h2, windows 11 26h1. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Heap-based buffer overflow in Windows Kernel allows an authorized attacker to elevate privileges locally.

Why this priority

High severity
EPSS top 8%: very likely to be exploited
Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	4.7% (top 8%)
CISA exploited list	No
Weakness	CWE-822
Published	2026-05-12
Last modified	2026-06-26

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-06-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-12 18:17 UTCPublished CVE record published
2026-06-26 05:16 UTCUpdated Record last modified

microsoft windows 11 24h2 UPGRADE

Affected: < 10.0.26100.8390

Fixed in: 10.0.26100.8390

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

microsoft windows 11 25h2 UPGRADE

Affected: < 10.0.26200.8390

Fixed in: 10.0.26200.8390

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

microsoft windows 11 26h1 UPGRADE

Affected: < 10.0.28000.2113

Fixed in: 10.0.28000.2113

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

microsoft windows server 2025 UPGRADE

Affected: < 10.0.26100.32772

Fixed in: 10.0.26100.32772

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

Fedora 46 · fzssh · FIXED · 1.4.0-2.fc46 · FEDORA-2026-8004fcd067 · source

sudo dnf upgrade --advisory=FEDORA-2026-8004fcd067

Windows Server 2025 (Server Core installation) · KB5087539 · FIXED · 10.0.26100.32860 · KB5087539 · source

Install KB5087539 via Windows Update, then verify: Get-HotFix -Id KB5087539

Windows Server 2025 · KB5087539 · FIXED · 10.0.26100.32860 · KB5087539 · source

Install KB5087539 via Windows Update, then verify: Get-HotFix -Id KB5087539

Windows Server 2025 (Server Core installation) · KB5087423 · FIXED · 10.0.26100.32772 · KB5087423 · source

Install KB5087423 via Windows Update, then verify: Get-HotFix -Id KB5087423

Windows Server 2025 · KB5087423 · FIXED · 10.0.26100.32772 · KB5087423 · source

Install KB5087423 via Windows Update, then verify: Get-HotFix -Id KB5087423

Windows 11 Version 25H2 for x64-based Systems · KB5089549 · FIXED · 10.0.26200.8457 · KB5089549 · source

Install KB5089549 via Windows Update, then verify: Get-HotFix -Id KB5089549

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: orinimron123/CVE-2026-40369-EXPLOIT (280 stars)
GitHub PoC: ZeroDayEvil/CVE-2026-40369-EXPLOIT (24 stars)
GitHub PoC: piffd0s/ntoskrnl-metadata (4 stars)

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-40369?

windows 11 24h2: upgrade to 10.0.26100.8390; windows 11 25h2: upgrade to 10.0.26200.8390; windows 11 26h1: upgrade to 10.0.28000.2113. Exact commands for each OS are on this page.

Is CVE-2026-40369 being exploited?

CVE-2026-40369 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-40369 affect?

CVE-2026-40369 affects windows 11 24h2, windows 11 25h2, windows 11 26h1. Severity is high (CVSS 7.8). Heap-based buffer overflow in Windows Kernel allows an authorized attacker to elevate privileges locally.

How urgent is CVE-2026-40369?

Priority 60/100. High severity; EPSS top 8%: very likely to be exploited; Public exploit reference; On your watchlist

Software pages

Windows vulnerabilities · Windows Server vulnerabilities

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References

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