dbcve.org
Windows 10 1607Operating system · Microsoft

CVE-2026-20844

HIGH · 7.4 CVSS v3.1 Published 2026-01-13
Fix available
A fix is available. Upgrade to 10.0.14393.8783 / 10.0.17763.8276 or later.
See remediation →
79/100
Remediation priority · High
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 Clipboard Server allows an unauthorized attacker to elevate privileges locally.

In the news

Third-party coverage
Trending covered by 1 outlet this week · latest 7mo ago

Surfaced from public web coverage — external links open in a new tab.

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 vulnerability in the Windows Clipboard Server allows a local attacker to exploit freed memory access, potentially executing arbitrary code with elevated privileges. This is a memory corruption issue in a core Windows service that can be exploited locally without authentication.

MitigationApply Microsoft security patches for this vulnerability once released. Until then, limit local system access to trusted administrators only and monitor for indicators of compromise targeting clipboard functionality.

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 1607Operating system
Affected:< 10.0.14393.8783
Windows 10 1809Operating system
Affected:< 10.0.17763.8276
Windows 10 21h2Operating system
Affected:< 10.0.19044.6809
Windows 10 22h2Operating system
Affected:< 10.0.19045.6809
Windows 11 23h2Operating system
Affected:< 10.0.22631.6491
Windows 11 24h2Operating system
Affected:< 10.0.26100.7623
Windows 11 25h2Operating system
Affected:< 10.0.26200.7623
Windows Server 2016Operating system
Affected:< 10.0.14393.8783

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

CVSS:3.1/AV:L/AC:H/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
    Run 'winver' from command prompt or 'systeminfo' to obtain the exact Windows build number (for example, 10.0.19045.6809)
    Affected if The build number falls below the fixed version for your Windows release: Windows 10 1607/Server 2016 < 10.0.14393.8783, Windows 10 1809 < 10.0.17763.8276, Windows 10 21h2 < 10.0.19044.6809, Windows 10 22h2 < 10.0.19045.6809, Windows 11 23h2 < 10.0.22631.6491, Windows 11 24h2 < 10.0.26100.7623, Windo
  2. Confirm Clipboard Server is accessible
    Verify the Windows Clipboard feature is available on the system; in Windows 10/11 the clipboard service runs as part of user session processes (ctfmon.exe or related components)
    Affected if The clipboard functionality is enabled and accessible to the local user context, as the vulnerability is exploitable locally without authentication
  3. Check for recent clipboard-related processes
    Run 'tasklist | findstr ctfmon' or check Task Manager for ctfmon.exe and other clipboard-related processes running in user sessions
    Affected if Clipboard processes are actively running, which provides the attack surface for the use-after-free vulnerability

You are affected if your Windows build number is lower than the fixed version for your specific Windows release and the Clipboard Server is accessible 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 10.0.14393.8783 / 10.0.17763.8276 / 10.0.19044.6809 or later
Fixed in 10.0.14393.878310.0.17763.827610.0.19044.6809
Interim mitigation

Apply Microsoft security patches for this vulnerability once released. Until then, limit local system access to trusted administrators only and monitor for indicators of compromise targeting clipboard functionality.

Recommended fix High confidence

Microsoft security update containing the fix for CVE-2026-20844 (install latest cumulative update for your Windows version)

  1. Identify current Windows version and build number by running 'winver' or 'systeminfo'
  2. Apply the relevant Microsoft security update for this CVE (typically a cumulative update)
  3. Restart the system when prompted to complete the update installation
  4. Verify the installed build matches or exceeds the fixed version for your Windows release: Windows 10 1607/Server 2016: 10.0.14393.8783, Windows 10 1809: 10.0.17763.8276, Windows 10 21h2: 10.0.19044.6809, Windows 10 22h2: 10.0.19045.6809, Windows 11 23h2: 10.0.22631.6491, Windows 11 24h2: 10.0.26100.7623, Windows 11 25h2: 10.0.26200.7623
Caveat Standard Windows update risks - update has been tested by Microsoft but test in staging if possible

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

Fix this in Windows 10 1607 Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing12.0 h
  • Review / QA4.0 h
40.0 hours of engineering $7,000
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $11,200.

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-2026-20844 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