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Windows 11 24h2Operating system · Microsoft

CVE-2026-21250

HIGH · 7.8 CVSS v3.1 Published 2026-02-10
Fix available
A fix is available. Upgrade to 10.0.25398.2149 / 10.0.26100.7781 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
Untrusted pointer dereference in Windows HTTP.sys 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 pointer dereference vulnerability in the Windows HTTP.sys kernel driver allows a locally authenticated attacker to manipulate memory pointers improperly, potentially executing code at elevated privilege levels. This is a privilege escalation flaw in a kernel-mode component that processes HTTP requests.

MitigationApply the Microsoft security update for CVE-2026-21250 to all affected Windows systems. As this is a kernel-level vulnerability in HTTP.sys, no workarounds exist—patching is the only 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 11 24h2Operating system
Affected:< 10.0.26100.7781
Windows 11 25h2Operating system
Affected:< 10.0.26200.7781
Windows Server 2022 23h2Operating system
Affected:< 10.0.25398.2149
Windows Server 2025Operating system
Affected:< 10.0.26100.32313

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 version
    Run 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to identify the installed Windows version and build number
    Affected if The version is Windows 11 24h2, Windows 11 25h2, Windows Server 2022 23h2, or Windows Server 2025 and the build number is below the fixed versions (26100.7781, 26200.7781, 25398.2149, or 26100.32313 respectively)
  2. Identify HTTP.sys driver file version
    Locate http.sys at C:\Windows\System32\drivers\http.sys, right-click and view Properties > Details, or run 'powershell (Get-Item C:\Windows\System32\drivers\http.sys).VersionInfo'
    Affected if The FileVersion is below 10.0.26100.7781 for Windows 11 24h2/Server 2025, below 10.0.26200.7781 for Windows 11 25h2, or below 10.0.25398.2149 for Windows Server 2022 23h2
  3. Verify HTTP service is in use
    Check if IIS, HTTP Service, or any service dependent on HTTP.sys is running via 'sc query http' or 'Get-Service http' in PowerShell
    Affected if The HTTP.sys driver is loaded and actively handling HTTP requests (IIS, HTTP Service, or other HTTP listeners are enabled)
  4. Confirm kernel driver loaded status
    Run 'driverquery /v | findstr http' or 'Get-ProcessDriver http' to see if http.sys is currently loaded in memory
    Affected if The http.sys driver is listed as running or loaded in the system driver list

A system is affected if it runs one of the listed Windows versions/builds AND http.sys is present, with a version lower than the fixed builds, especially when HTTP services are enabled.

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 10.0.25398.2149 / 10.0.26100.7781 / 10.0.26100.32313 or later
Fixed in 10.0.25398.214910.0.26100.778110.0.26100.32313
Interim mitigation

Apply the Microsoft security update for CVE-2026-21250 to all affected Windows systems. As this is a kernel-level vulnerability in HTTP.sys, no workarounds exist—patching is the only remediation.

Recommended fix High confidence

Install Windows updates to reach build 10.0.26100.7781 or higher for Win11 24h2; 10.0.26200.7781 or higher for Win11 25h2; 10.0.25398.2149 or higher for Server 2022 23h2; 10.0.26100.32313 or higher for Server 2025

  1. Open Settings > Windows Update and check for updates
  2. If automatic updates don't show the fix, manually check the Microsoft Update Catalog for the KB article corresponding to this CVE (CVE-2026-21250)
  3. Download and install the appropriate KB patch for your Windows version
  4. Restart the system to apply the kernel-level changes
  5. Verify the installed build number matches or exceeds the fixed version: Windows 11 24h2 should be >=10.0.26100.7781, Windows 11 25h2 >=10.0.26200.7781, Windows Server 2022 23h2 >=10.0.25398.2149, or Windows Server 2025 >=10.0.26100.32313
Caveat Standard Windows cumulative update; test related Windows services (especially IIS/HTTP services that use HTTP.sys) after patching

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

Fix this in Windows 11 24h2 Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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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-2026-21250 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