dbcve.org
Windows 10 1607Operating system · Microsoft

CVE-2026-40377

HIGH · 7.8 CVSS v3.1 Published 2026-05-12
Fix available
A fix is available. Upgrade to 10.0.14393.9140 / 10.0.17763.8755 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
Heap-based buffer overflow in Windows Cryptographic Services 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

Heap-based buffer overflow vulnerability in Windows Cryptographic Services allows a locally authorized attacker to execute arbitrary code with elevated privileges via crafted input that overflows heap memory allocations in the cryptographic service components.

MitigationApply Microsoft security updates for Windows Cryptographic Services when available; prioritize patching systems with direct user access and validate cryptographic functions (certificate operations, signing, encryption) post-patch.

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:< 10.0.14393.9140
Windows 10 1809Operating system
Affected:< 10.0.17763.8755
Windows 10 21h2Operating system
Affected:< 10.0.19044.7291
Windows 10 22h2Operating system
Affected:< 10.0.19045.7291
Windows 11 23h2Operating system
Affected:< 10.0.22631.7079
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

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. Check Windows build version
    Open Command Prompt or PowerShell and run 'winver' or 'systeminfo | findstr /B /C:"OS Version"' to obtain the full build number including the 4-digit revision (e.g., 10.0.19045.7291)
    Affected if The installed build number is lower than any of the following thresholds: 14393.9140, 17763.8755, 19044.7291, 19045.7291, 22631.7079, 26100.8390, 26200.8390, or 28000.2113 depending on your Windows release
  2. Confirm Windows release version
    Run 'winver' to identify whether you are on Windows 10 1607, 1809, 21h2, 22h2, or Windows 11 23h2, 24h2, 25h2, or 26h1
    Affected if The release corresponds to an affected build range with a version lower than the threshold listed for that release in the CVE
  3. Verify Cryptographic Services are enabled
    Open Services console (services.msc) and locate 'Cryptographic Services', or run 'Get-Service CryptSvc' in PowerShell to check if the service is running
    Affected if The Cryptographic Services service is present and running (this is the default state on Windows systems)

You are affected if your Windows build number is lower than the threshold for your specific Windows release and the Cryptographic Services component is enabled, which is the default configuration.

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 10.0.14393.9140 / 10.0.17763.8755 / 10.0.19044.7291 or later
Fixed in 10.0.14393.914010.0.17763.875510.0.19044.7291
Interim mitigation

Apply Microsoft security updates for Windows Cryptographic Services when available; prioritize patching systems with direct user access and validate cryptographic functions (certificate operations, signing, encryption) post-patch.

Recommended fix High confidence

Windows 10 1607: 10.0.14393.9140 or later | Windows 10 1809: 10.0.17763.8755 or later | Windows 10 21h2: 10.0.19044.7291 or later | Windows 10 22h2: 10.0.19045.7291 or later | Windows 11 23h2: 10.0.22631.7079 or later | Windows 11 24h2: 10.0.26100.8390 or later | Windows 11 25h2: 10.0.26200.8390 or

  1. 1. Identify the current Windows version by running 'winver' or 'systeminfo' in Command Prompt
  2. 2. Determine which Windows 10 or 11 release channel you are on (e.g., 1607, 1809, 21h2, 22h2, 23h2, 24h2, 25h2, 26h1)
  3. 3. Open Windows Update: Settings > Update & Security > Windows Update
  4. 4. Click 'Check for updates' to download and install the latest security updates
  5. 5. Alternatively, manually install the specific KB update from Microsoft Update Catalog matching your Windows version
  6. 6. Restart the system when prompted to complete the installation
  7. 7. Verify the update was installed by checking 'Update history' in Windows Update settings
  8. 8. Confirm the installed build number matches or exceeds the fixed version for your release (e.g., run 'winver' to verify)
Caveat Standard Windows update; no breaking changes expected for this security patch

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

Fix this in Windows 10 1607 Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA3.0 h
21.0 hours of engineering $3,680
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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-2026-40377 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