Windows Server 2012Operating system · Microsoft

CVE-2026-35420

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

NVD · unedited

Heap-based buffer overflow in Windows Kernel allows an authorized attacker to elevate privileges locally.

Technical summary

dbcve analysis · moderate confidence

A heap-based buffer overflow vulnerability exists in the Windows Kernel that allows a locally authorized attacker to elevate their privileges to higher levels. The vulnerability stems from improper bounds checking in kernel-mode memory operations, enabling an attacker with local access to potentially execute arbitrary code in kernel context.

MitigationApply Microsoft security updates immediately once available. Ensure systems are fully patched and follow least-privilege principles to limit local attack surface.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions

NVD · CPE data

Windows Server 2012Operating system

Affected:all versions= r2

Windows Server 2016Operating system

Affected:< 10.0.14393.9140

Windows Server 2019Operating system

Affected:< 10.0.17763.8755

Windows Server 2022Operating system

Affected:< 10.0.20348.5074

Windows Server 2022 23h2Operating system

Affected:< 10.0.25398.2330

Windows Server 2025Operating system

Affected:< 10.0.26100.32772

CVSS breakdown

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?

dbcve checks

Work through these to decide whether this CVE applies to you.

Check Windows Server version and build number

Run 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to obtain the exact Windows version and build number

Affected if The build number falls below the fixed versions (Server 2016 < 10.0.14393.9140, Server 2019 < 10.0.17763.8755, Server 2022 < 10.0.20348.5074, Server 2022 23H2 < 10.0.25398.2330, Server 2025 < 10.0.26100.32772) or is Server 2012 R2 (all versions)
Confirm Windows edition is affected

Verify the system is running one of the affected Windows Server editions: 2012 R2, 2016, 2019, 2022, 2022 23H2, or 2025 using 'winver' or checking System Properties

Affected if The system is running Windows Server 2012 R2, 2016, 2019, 2022, 2022 23H2, or 2025
Verify kernel patch level

Run 'systeminfo' and check the 'Hotfix(s)' section, or query the registry at HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Component Based Servicing\Packages for installed security update KB numbers matching the CVE release month

Affected if The installed security updates do NOT include the specific KB patch for CVE-2026-35420 or the system shows a build number below the fixed thresholds

A system is affected if it runs Windows Server 2012 R2 (any build) or any version of Windows Server 2016/2019/2022/2022 23H2/2025 with a build number lower than the fixed thresholds AND missing the corresponding security update.

Generated from the published advisory. Verify against your own configuration.

Remediation

dbcve · scoped

Upgrade available Upgrade to 10.0.14393.9140 / 10.0.17763.8755 / 10.0.20348.5074 or later

Fixed in 10.0.14393.914010.0.17763.875510.0.20348.5074

Interim mitigation

Apply Microsoft security updates immediately once available. Ensure systems are fully patched and follow least-privilege principles to limit local attack surface.

Recommended fix High confidence

Upgrade to the minimum fixed build for your Windows Server version: Server 2016 to 10.0.14393.9140, Server 2019 to 10.0.17763.8755, Server 2022 to 10.0.20348.5074, Server 2022 23h2 to 10.0.25398.2330, or Server 2025 to 10.0.26100.32772. Windows Server 2012 has no patch available and requires migrati

Identify the current Windows Server version by running 'winver' or 'systeminfo' in Command Prompt
Determine which build version is currently installed (e.g., for Server 2019, check if below 10.0.17763.8755)
For Windows Server 2012: Note that this version is end-of-life with no security updates available; migration to a supported Windows Server version is required
For Windows Server 2016 and later: Open Windows Update via Settings > Update & Security > Windows Update
Check for updates and install the cumulative security update containing the fix for CVE-2026-35420
Reboot the server after applying the update
Verify the installed version meets or exceeds the minimum fixed build: Server 2016 requires 10.0.14393.9140, Server 2019 requires 10.0.17763.8755, Server 2022 requires 10.0.20348.5074, Server 2022 23h2 requires 10.0.25398.2330, Server 2025 requires 10.0.26100.32772
Alternatively, use Windows Server Update Services (WSUS) or Microsoft Endpoint Configuration Manager to deploy the security update enterprise-wide

Caveat Standard Windows cumulative update apply; verify application compatibility before production deployment. Windows Server 2012 has reached end-of-life and cannot receive security updates.

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

Fix this in Windows Server 2012 Scoped from the published advisory

Consultation4.0 h
Implementation8.0 h
Testing12.0 h
Review / QA6.0 h

30.0 hours of engineering $5,120

Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $8,192.

Scan for this in your stack

Free · runs locally

dbcve dependency scanner

Check whether your project pulls in CVE-2026-35420 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

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References

Primary sources

msrc.microsoft.comVendor Advisory
nvd.nist.govNVD record

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-35420 in production — separate from our analysis above.

Notes0 Guidelines

Know something about CVE-2026-35420?

The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.

The version that genuinely resolved it — not the one the vendor claimed
A config change or rule that shut the vector down
A gotcha in the upgrade path that cost you an afternoon

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

At a glance

A fix existsUpgrade to 10.0.14393.9140 / 10.0.17763.8755 or later

Severity 7.8 High

Exploit likelihood EPSS, next 30 days 0.3%

Affects: Windows Server 2012

Remediation

A high-priority fix

Fix this in Windows Server 2012 30 hrs · High

Typical engagement from $5,120

Get a fix See the full breakdown ↓

A high-priority vulnerability. Send your environment and a specialist will scope CVE-2026-35420 and return a fixed quote and timeline.

You’ll deal with our team directly and deploy the reviewed fix to staging first — never straight to production.

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.

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.

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.

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.

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.

Check your environment

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.

Scan for this in your stack

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Practitioner notes

No notes yet

Official description

Technical summary

Affected products & versions

CVSS breakdown

Am I affected?

Remediation

References