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Windows 11 23h2Operating system · Microsoft

CVE-2026-45657

CRITICAL · 9.8 CVSS v3.1 Published 2026-06-09
Fix available
A fix is available. Upgrade to 10.0.20348.5256 / 10.0.22631.7219 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Use after free in Windows Kernel allows an unauthorized attacker to execute code over a network.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A Use After Free (UAF) vulnerability in the Windows Kernel allows an unauthorized remote attacker to execute arbitrary code. The flaw involves memory corruption where the kernel fails to properly manage object lifetime, potentially enabling an attacker to manipulate freed memory and escalate privileges or execute code in kernel context.

MitigationApply Microsoft security updates immediately as they become available; prioritize network-facing systems given the remote exploitation vector indicated by CVSS 9.8.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Windows 11 23h2Operating system
Affected:< 10.0.22631.7219
Windows 11 24h2Operating system
Affected:< 10.0.26100.8655
Windows 11 25h2Operating system
Affected:< 10.0.26200.8655
Windows 11 26h1Operating system
Affected:< 10.0.28000.2269
Windows Server 2022Operating system
Affected:< 10.0.20348.5256
Windows Server 2025Operating system
Affected:< 10.0.26100.32995

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check Windows version and build number
    Open Command Prompt and run `winver` to display the OS version and build, or run `systeminfo | findstr /B /C:"OS Name" /C:"OS Version"`
    Affected if The build number displayed is lower than the affected version for your Windows edition
  2. Identify exact build number on Windows 11/Server
    Run `ver` in Command Prompt or check `HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion` in Registry Editor for the CurrentBuild and DisplayVersion values
    Affected if The CurrentBuild number is below 22631.7219 (23h2), 26100.8655 (24h2), 26200.8655 (25h2), 28000.2269 (26h1), 20348.5256 (Server 2022), or 26100.32995 (Server 2025)
  3. Confirm Windows edition matches affected products
    Run `systeminfo | findstr "Product"` or check System Properties to verify you are running Windows 11 (any h2 version) or Windows Server 2022/2025
    Affected if The edition is Windows 11 or Windows Server 2022/2025 and the build number falls into any of the affected ranges
  4. Check for installed security updates
    Open Settings > Windows Update > Update history, or run `wmic qfe list` to list installed hotfixes. Look for KB entries dated after the patch release for this CVE
    Affected if No specific security update for this CVE is installed and the version falls within the affected build ranges

You are affected if your Windows 11 or Windows Server 2022/2025 system build number is lower than the thresholds listed for your specific version and no security patch for this vulnerability has been applied.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 10.0.20348.5256 / 10.0.22631.7219 / 10.0.26100.8655 or later
Fixed in 10.0.20348.525610.0.22631.721910.0.26100.8655
Interim mitigation

Apply Microsoft security updates immediately as they become available; prioritize network-facing systems given the remote exploitation vector indicated by CVSS 9.8.

Recommended fix High confidence

Windows 11 23h2: build 10.0.22631.7219 | Windows 11 24h2: build 10.0.26100.8655 | Windows 11 25h2: build 10.0.26200.8655 | Windows 11 26h1: build 10.0.28000.2269 | Windows Server 2022: build 10.0.20348.5256 | Windows Server 2025: build 10.0.26100.32995

  1. Open Settings > System > Windows Update and check for updates
  2. Install all pending Windows security updates to reach the fixed build version
  3. Alternatively, verify current build by running 'winver' in Run dialog
  4. Manually update to KB5xxxxx (specific security update for this CVE) from Microsoft Update Catalog if automatic updates don't provide the fix
  5. Restart the system after applying updates
Caveat Standard Windows update process; no expected breaking changes for this kernel patch

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Windows 11 23h2 Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing8.0 h
  • Review / QA4.0 h
18.0 hours of engineering $3,080
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,928.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-45657 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data