dbcve.org
Windows 10 1607Operating system · Microsoft

CVE-2026-21253

HIGH · 7.0 CVSS v3.1 Published 2026-02-10
Fix available
A fix is available. Upgrade to 10.0.14393.8868 / 10.0.17763.8389 or later.
See remediation →
72/100
Remediation priority · Elevated
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 Mailslot File System 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 Use-After-Free vulnerability in the Windows Mailslot File System allows a local authorized attacker to manipulate freed memory and elevate privileges to higher permission levels.

MitigationApply Microsoft security updates addressing CVE-2026-21253 once released, as this is a kernel-level vulnerability requiring vendor patch remediation.

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:< 10.0.14393.8868
Windows 10 1809Operating system
Affected:< 10.0.17763.8389
Windows 10 21h2Operating system
Affected:< 10.0.19044.6937
Windows 10 22h2Operating system
Affected:< 10.0.19045.6937
Windows 11 23h2Operating system
Affected:< 10.0.22631.6649
Windows 11 24h2Operating system
Affected:< 10.0.26100.7781
Windows 11 25h2Operating system
Affected:< 10.0.26200.7781
Windows Server 2012Operating system
Affected:all versions= r2

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
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:H/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. Check Windows build version
    Run 'winver' or 'systeminfo' from command prompt and note the exact build number displayed (e.g., 10.0.19045.6937 for Windows 10 22h2)
    Affected if The build number falls below the fixed version for your Windows release: 14393.8868 (1607), 17763.8389 (1809), 19044.6937 (21h2), 19045.6937 (22h2), 22631.6649 (23h2), 26100.7781 (24h2), 26200.7781 (25h2), or any Server 2012/R2 build
  2. Confirm Windows edition
    Run 'winver' or check System Properties to identify whether the system is Windows 10, Windows 11, or Windows Server 2012/R2
    Affected if Running an affected edition and version combination as listed in the CVE
  3. Verify kernel patch status
    Check Windows Update history for security updates installed after the CVE disclosure date, or run 'Get-HotFix' in PowerShell to list installed patches
    Affected if No security update addressing CVE-2026-21253 has been installed, and the version falls within the vulnerable range

The system is affected if running any Windows 10/11 version or Windows Server 2012/R2 build below the specific fixed build numbers listed in the CVE, indicating the kernel mailslot vulnerability remains unpatched.

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 10.0.14393.8868 / 10.0.17763.8389 / 10.0.19044.6937 or later
Fixed in 10.0.14393.886810.0.17763.838910.0.19044.6937
Interim mitigation

Apply Microsoft security updates addressing CVE-2026-21253 once released, as this is a kernel-level vulnerability requiring vendor patch remediation.

Recommended fix High confidence

Upgrade to Windows 10 1607 (10.0.14393.8868), 1809 (10.0.17763.8389), 21h2 (10.0.19044.6937), 22h2 (10.0.19045.6937); Windows 11 23h2 (10.0.22631.6649), 24h2 (10.0.26100.7781), 25h2 (10.0.26200.7781); or Windows Server 2012 R2 with latest security updates

  1. 1. Identify the current Windows version by running `winver` or checking System Properties
  2. 2. For Windows 10: Navigate to Settings > Update & Security > Windows Update and check for updates
  3. 3. For Windows 11: Navigate to Settings > Windows Update and check for updates
  4. 4. Install all cumulative updates and security patches provided through Windows Update
  5. 5. For Windows Server 2012/R2: Use Server Manager or Windows Update to install all available security updates
  6. 6. Restart the system after updates are installed
  7. 7. Verify the installed version matches or exceeds the fixed version for your Windows release
Caveat Standard Windows update process; may require restart; ensure backups and compatibility testing for business-critical applications

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

Fix this in Windows 10 1607 Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,720
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,752.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-21253 — 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-2026-21253 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