dbcve.org
Windows 10 1607Operating system · Microsoft

CVE-2026-42903

MEDIUM · 6.5 CVSS v3.1 Published 2026-06-09
Fix available
A fix is available. Upgrade to 10.0.14393.9234 / 10.0.17763.8880 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable 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
Null pointer dereference in Windows Kerberos allows an authorized attacker to deny service over a network.

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

This is a null pointer dereference vulnerability in Windows Kerberos implementation that allows an authenticated attacker to cause a denial of service by crashing the Kerberos service or authentication process.

MitigationApply Microsoft security updates for Windows Kerberos when available. Ensure Windows servers and domain controllers are regularly patched.

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:< 10.0.14393.9234
Windows 10 1809Operating system
Affected:< 10.0.17763.8880
Windows 10 21h2Operating system
Affected:< 10.0.19044.7417
Windows 10 22h2Operating system
Affected:< 10.0.19045.7417
Windows 11 23h2Operating system
Affected:< 10.0.22631.7219
Windows 11 24h2Operating system
Affected:< 10.0.26100.8655
Windows 11 25h2Operating system
Affected:< 10.0.26200.8655
Windows 11 26h1Operating system
Affected:< 10.0.28000.2269

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

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/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. Identify Windows version and build number
    Run 'winver' from Command Prompt or check 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to obtain the exact Windows build number.
    Affected if The build number is lower than any of these: 14393.9234 (Win10 1607), 17763.8880 (Win10 1809), 19044.7417 (Win10 21h2), 19045.7417 (Win10 22h2), 22631.7219 (Win11 23h2), 26100.8655 (Win11 24h2), 26200.8655 (Win11 25h2), 28000.2269 (Win11 26h1).
  2. Confirm Kerberos service is running
    Run 'sc query kdc' (Key Distribution Center) on domain controllers or 'netstat -an | findstr "88"' on any system to check if Kerberos ports 88/TCP or 88/UDP are listening.
    Affected if The Kerberos service (KDC) is running or ports 88/TCP and 88/UDP are in LISTENING state, indicating the Kerberos feature is enabled.
  3. Check if system participates in Active Directory domain
    Run 'systeminfo | findstr "Domain"' or 'whoami /groups' to see if the machine is joined to a domain, which enables Kerberos authentication.
    Affected if The system is domain-joined, meaning Kerberos is the primary authentication protocol and is actively used.
  4. Verify patch installation status
    Run 'powershell Get-HotFix | where {$_.HotFixID -like "KB*"} | sort InstalledOn -Descending | select -First 10' to list recently installed patches, or check Windows Update history for security updates released for this CVE.
    Affected if The security update addressing CVE-2026-42903 is not installed and the Windows version falls within the affected build ranges.

A system is affected if it runs a Windows version with a build number below the fixed thresholds AND has Kerberos enabled (domain-joined or KDC service running), making it reachable to authenticated attackers on the network.

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 10.0.14393.9234 / 10.0.17763.8880 / 10.0.19044.7417 or later
Fixed in 10.0.14393.923410.0.17763.888010.0.19044.7417
Interim mitigation

Apply Microsoft security updates for Windows Kerberos when available. Ensure Windows servers and domain controllers are regularly patched.

Recommended fix High confidence

Install the latest Windows security updates (monthly patch Tuesday or later) to reach the fixed build version for your Windows release

  1. Open Settings > Update & Security > Windows Update
  2. Click 'Check for updates' to download and install the latest security updates
  3. Ensure the update includes the KB patch for this vulnerability (check Windows Update history for the specific KB number)
  4. Restart the system after updates are installed
  5. Verify the installed build version matches or exceeds the fixed build: Windows 10 1607: 10.0.14393.9234, Windows 10 1809: 10.0.17763.8880, Windows 10 21h2: 10.0.19044.7417, Windows 10 22h2: 10.0.19045.7417, Windows 11 23h2: 10.0.22631.7219, Windows 11 24h2: 10.0.26100.8655, Windows 11 25h2: 10.0.26200.8655, Windows 11 26h1: 10.0.28000.2269
Caveat Standard Windows update risks apply - ensure backups and compatibility testing for critical systems

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
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
13.0 hours of engineering $2,330
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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-2026-42903 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