dbcve.org
Windows 10 1809Operating system · Microsoft

CVE-2026-42991

HIGH · 7.8 CVSS v3.1 Published 2026-06-09
Fix available
A fix is available. Upgrade to 10.0.17763.8880 / 10.0.19044.7417 or later.
See remediation →
80/100
Remediation priority · High
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
Concurrent execution using shared resource with improper synchronization ('race condition') in Windows Push Notifications allows an authorized attacker to elevate privileges locally.

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 race condition vulnerability exists in Windows Push Notifications where improper synchronization of shared resources allows a locally authorized attacker to escalate privileges. The vulnerability stems from concurrent execution issues in the notification handling mechanism.

MitigationApply the appropriate Microsoft security update for Windows Push Notifications when available. Ensure systems are patched through standard Windows Update processes.

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 10 1809Operating system
Affected:< 10.0.17763.8880
Windows 10 21h2Operating system
Affected:< 10.0.19044.7417
Windows 10 22h2Operating system
Affected:< 10.0.19045.7417
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 2019Operating system
Affected:< 10.0.17763.8880

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
Local
Complexity
High
Privileges
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/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 or PowerShell and run 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"'. Alternatively, run 'ver' in cmd or '[System.Environment]::OSVersion.Version' in PowerShell.
    Affected if The build number is less than the fixed versions: 17763.8880 (Windows 10 1809/Server 2019), 19044.7417 (Windows 10 21h2), 19045.7417 (Windows 10 22h2), 22631.7219 (Windows 11 23h2), 26100.8655 (Windows 11 24h2/25h2), 26200.8655 (Windows 11 25h2), or 28000.2269 (Windows 11 26h1).
  2. Confirm exact build via registry
    Run 'reg query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion" /v CurrentBuildNumber' and '/v UBR' in Command Prompt to get the full build number (CurrentBuildNumber.UBR).
    Affected if The combined build number (CurrentBuild.UBR) falls below the thresholds listed above for your Windows release.
  3. Identify Windows release name
    Run 'winver' and note the release (such as "Version 22H2" or "23H2") or check the registry key at 'HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion' for the 'DisplayVersion' value.
    Affected if The release matches any of the affected versions listed in the CVE (1809, 21h2, 22h2, 23h2, 24h2, 25h2, 26h1, or Server 2019) AND the build is below the patched threshold.
  4. Verify Push Notifications service status
    Check if the Windows Push Notification Service (WPNService) is running: run 'Get-Service WPNService' in PowerShell or 'sc query WPNService' in Command Prompt.
    Affected if The WPNService is present and running. This is the component with the race condition vulnerability.

You are affected if your Windows build number is below the patched threshold for your specific Windows release AND the WPNService is available on your system.

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 10.0.17763.8880 / 10.0.19044.7417 / 10.0.19045.7417 or later
Fixed in 10.0.17763.888010.0.19044.741710.0.19045.7417
Interim mitigation

Apply the appropriate Microsoft security update for Windows Push Notifications when available. Ensure systems are patched through standard Windows Update processes.

Recommended fix High confidence

Windows 10 1809: 10.0.17763.8880 or later | Windows 10 21h2: 10.0.19044.7417 or later | Windows 10 22h2: 10.0.19045.7417 or later | Windows 11 23h2: 10.0.22631.7219 or later | Windows 11 24h2: 10.0.26100.8655 or later | Windows 11 25h2: 10.0.26200.8655 or later | Windows 11 26h1: 10.0.28000.2269 or

  1. Identify the current Windows build version by running `winver` or `systeminfo` in Command Prompt
  2. Determine which Windows version and build you are running from the affected list (Windows 10 1809, 10 21h2, 10 22h2, Windows 11 23h2, 24h2, 25h2, 26h1, or Windows Server 2019)
  3. Apply the Microsoft security update for CVE-2026-42991 via Windows Update: Open Settings > Update & Security > Windows Update and select 'Check for updates'
  4. Alternatively, manually download and install the security update from the Microsoft Update Catalog by searching for the CVE number or KB article associated with this vulnerability
  5. Verify the update was installed successfully and the system build matches or exceeds the fixed version for your Windows release
Caveat Standard Windows security update; no expected breaking changes for most users

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

Fix this in Windows 10 1809 Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,560
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,096.

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-2026-42991 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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