dbcve.org
Windows 11 24h2Operating system · Microsoft

CVE-2026-33840

HIGH · 7.8 CVSS v3.1 Published 2026-05-12
Fix available
A fix is available. Upgrade to 10.0.26100.8390 / 10.0.26100.32772 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
Use after free in Windows Win32K - ICOMP 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 · high confidence

Use-after-free vulnerability in the Windows Win32K kernel subsystem's ICOMP component allows a locally authorized attacker to elevate privileges to SYSTEM level by exploiting freed memory that is still accessed after deallocation.

MitigationApply Microsoft security updates for this vulnerability through standard Windows patch management; until patches are available, restrict local administrative access and monitor for indicators of compromise targeting privilege escalation.

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 24h2Operating system
Affected:< 10.0.26100.8390
Windows 11 25h2Operating system
Affected:< 10.0.26200.8390
Windows 11 26h1Operating system
Affected:< 10.0.28000.2113
Windows Server 2025Operating system
Affected:< 10.0.26100.32772

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
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/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. Determine Windows build version
    Run 'winver' from command prompt or execute 'systeminfo' and look at the 'OS Version' line. Alternatively, run 'powershell [Environment]::OSVersion.Version' or 'winmgmt /salva /getversion' to get the exact build number.
    Affected if The displayed build number falls below the affected thresholds (for 24h2: below 10.0.26100.8390; for 25h2: below 10.0.26200.8390; for 26h1: below 10.0.28000.2113; for Server 2025: below 10.0.26100.32772)
  2. Confirm Windows product edition
    Run 'winver' or check System Properties to verify if the system is Windows 11 (versions 24h2, 25h2, or 26h1) or Windows Server 2025. The build number alone is not sufficient as different Windows releases may share similar build numbers.
    Affected if The system is Windows 11 24h2, 25h2, 26h1, or Windows Server 2025 and the build number is below the respective threshold for that release.
  3. Verify Win32K kernel driver is present
    Check that win32k.sys exists and is loaded. Run 'driverquery /v | findstr win32k' or checkHKLM\SYSTEM\CurrentControlSet\Services\Win32k in the registry. The driver is typically located at C:\Windows\System32\drivers\win32k.sys.
    Affected if The win32k.sys driver is loaded (which is default on Windows 11 and Server 2025 GUI installations) - this is required for the ICOMP vulnerability to be exploitable.
  4. Check current user privileges
    Run 'whoami /priv' or 'whoami /groups' to determine if the current user has administrative or elevated privileges. CVE-2026-33840 requires a locally authorized (authenticated) attacker.
    Affected if The user context is a local administrator or has SeImpersonatePrivilege/SeDebugPrivilege, meaning an attacker with these privileges could attempt exploitation.

A system is affected if it runs Windows 11 24h2/25h2/26h1 or Windows Server 2025 with a build number below the specified thresholds and has the Win32K subsystem loaded (standard on GUI-enabled Windows installations).

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 10.0.26100.8390 / 10.0.26100.32772 / 10.0.26200.8390 or later
Fixed in 10.0.26100.839010.0.26100.3277210.0.26200.8390
Interim mitigation

Apply Microsoft security updates for this vulnerability through standard Windows patch management; until patches are available, restrict local administrative access and monitor for indicators of compromise targeting privilege escalation.

Recommended fix High confidence

Windows 11 24h2 build 10.0.26100.8390+ | Windows 11 25h2 build 10.0.26200.8390+ | Windows 11 26h1 build 10.0.28000.2113+ | Windows Server 2025 build 10.0.26100.32772+

  1. Open Settings > System > Windows Update and check for updates
  2. Identify your Windows version by running 'winver' (24h2, 25h2, 26h1, or Server 2025)
  3. Install all available Windows cumulative security updates
  4. Verify the build number meets or exceeds: Windows 11 24h2 requires 10.0.26100.8390, 25h2 requires 10.0.26200.8390, 26h1 requires 10.0.28000.2113, Server 2025 requires 10.0.26100.32772
  5. Reboot the system to apply the kernel-level patch
  6. Confirm successful patching by checking the build number again with 'winver'
Caveat Standard Windows cumulative security updates typically have minimal compatibility impact; ensure critical applications are backed up and tested in a staging environment before production deployment

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

Fix this in Windows 11 24h2 Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-33840 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2026-33840 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