dbcve.org
Windows 10 1507Operating system · Microsoft

CVE-2025-21191

HIGH · 7.0 CVSS v3.1 Published 2025-04-08
Fix available
A fix is available. Upgrade to 10.0.10240.20978 / 10.0.14393.7969 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
Time-of-check time-of-use (toctou) race condition in Windows Local Security Authority (LSA) 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 time-of-check time-of-use (TOCTOU) race condition exists in Windows Local Security Authority (LSA), the component responsible for enforcing security policy on Windows systems. An authorized local attacker can exploit the race between security checks and their application to elevate privileges to a higher level.

MitigationApply Microsoft security updates for CVE-2025-21191 as soon as they become available. Prioritize domain controllers and systems with sensitive data or privileged users.

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 1507Operating system
Affected:< 10.0.10240.20978
Windows 10 1607Operating system
Affected:< 10.0.14393.7969
Windows 10 1809Operating system
Affected:< 10.0.17763.7136
Windows 10 21h2Operating system
Affected:< 10.0.19044.5737
Windows 10 22h2Operating system
Affected:< 10.0.19045.5737
Windows 11 22h2Operating system
Affected:< 10.0.22621.5189
Windows 11 23h2Operating system
Affected:< 10.0.22631.5189
Windows 11 24h2Operating system
Affected:< 10.0.26100.3775

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. Identify Windows edition and build number
    Open Command Prompt or PowerShell and run: `winver` or `systeminfo | findstr /B /C:"OS Name" /C:"OS Version"`. Alternatively, run `winver` to see the full build number.
    Affected if Running any of the listed Windows editions (10 1507, 10 1607, 10 1809, 10 21h2, 10 22h2, 11 22h2, 11 23h2, 11 24h2)
  2. Compare build number against affected thresholds
    Note the full build number (for example, 10.0.19045.5007). Look up the specific threshold for your Windows edition from the CVE details: 1507 requires >=10.0.10240.20978, 1607 requires >=10.0.14393.7969, 1809 requires >=10.0.17763.7136, 21h2 requires >=10.0.19044.5737, 22h2 requires >=10.0.19045.5737, 11 22h2 requires >=10.0.22621.5189, 11 23h2 requires >=10.0.22631.5189, 11 24h2 requires >=10.0.26100.3775.
    Affected if The installed build number is lower than the required threshold for your specific Windows edition and branch

You are affected if you are running any of the listed Windows 10 or Windows 11 editions with a build number below the corresponding threshold for that edition.

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 10.0.10240.20978 / 10.0.14393.7969 / 10.0.17763.7136 or later
Fixed in 10.0.10240.2097810.0.14393.796910.0.17763.7136
Interim mitigation

Apply Microsoft security updates for CVE-2025-21191 as soon as they become available. Prioritize domain controllers and systems with sensitive data or privileged users.

Recommended fix High confidence

Install the relevant Windows security update; for each affected version, update to: Win10 1507 to 10.0.10240.20978, Win10 1607 to 10.0.14393.7969, Win10 1809 to 10.0.17763.7136, Win10 21h2 to 10.0.19044.5737, Win10 22h2 to 10.0.19045.5737, Win11 22h2 to 10.0.22621.5189, Win11 23h2 to 10.0.22631.5189

  1. Open Windows Update by pressing Win + I and navigating to Update & Security > Windows Update
  2. Click 'Check for updates' to scan for available updates
  3. Install all pending security updates, particularly the update containing the CVE-2025-21191 fix
  4. If automatic updates are disabled, manually download the specific security update from the Microsoft Update Catalog matching your Windows version and KB number
  5. Restart the system after installing the updates to ensure the LSA patch takes effect
  6. Verify the installed build version matches or exceeds the fixed version for your Windows release using 'winver' command
Caveat None expected; this is a security patch for a local privilege escalation flaw in LSA

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

Fix this in Windows 10 1507 Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.

Scan for this in your stack

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dbcve dependency scanner

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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-2025-21191 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