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Windows 11 24h2Operating system · Microsoft

CVE-2025-59257

MEDIUM · 6.5 CVSS v3.1 Published 2025-10-14
Fix available
A fix is available. Upgrade to 10.0.25398.1913 / 10.0.26100.6899 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
Improper validation of specified type of input in Windows Local Session Manager (LSM) 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

Improper input validation in Windows Local Session Manager (LSM) allows an authenticated attacker to send specially crafted network requests that cause a denial of service, potentially crashing the LSM service and disrupting user sessions.

MitigationApply the Microsoft security update for CVE-2025-59257 through Windows Update or your organization's patch management process to address the input validation flaw in LSM.

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:< 10.0.26100.6899
Windows 11 25h2Operating system
Affected:< 10.0.26200.6899
Windows Server 2022 23h2Operating system
Affected:< 10.0.25398.1913
Windows Server 2025Operating system
Affected:<= 10.0.26100.6899

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. Check installed Windows version
    Run 'winver' from command prompt, or use 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' or 'Get-ComputerInfo WindowsVersion' in PowerShell
    Affected if The version displayed falls within any of these ranges: Windows 11 24h2 < 10.0.26100.6899, Windows 11 25h2 < 10.0.26200.6899, Windows Server 2022 23h2 < 10.0.25398.1913, or Windows Server 2025 <= 10.0.26100.6899
  2. Confirm LSM service status
    Open Services (services.msc) and locate 'Local Session Manager' service, or run 'Get-Service -Name LSM' in PowerShell
    Affected if The Local Session Manager service exists and is running on the system (this is the component vulnerable to the flaw)
  3. Assess network exposure
    Review network configuration: check if the system is domain-joined, has remote access enabled, or is exposed to untrusted networks. Use 'Get-NetConnectionProfile' in PowerShell to see network categories
    Affected if The system is on a domain network or has remote network connectivity, as the attack vector involves sending specially crafted network requests to LSM

If the installed Windows version matches any of the affected version ranges AND the Local Session Manager service is running on a network-connected system, the environment is potentially affected by this CVE.

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 10.0.25398.1913 / 10.0.26100.6899 / 10.0.26200.6899 or later
Fixed in 10.0.25398.191310.0.26100.689910.0.26200.6899
Interim mitigation

Apply the Microsoft security update for CVE-2025-59257 through Windows Update or your organization's patch management process to address the input validation flaw in LSM.

Recommended fix High confidence

Windows 11 24h2: build 10.0.26100.6899 or later | Windows 11 25h2: build 10.0.26200.6899 or later | Windows Server 2022 23h2: build 10.0.25398.1913 or later | Windows Server 2025: build greater than 10.0.26100.6899

  1. Verify current Windows build version by running 'winver' or 'systeminfo' in Command Prompt
  2. Open Windows Settings > Update & Security > Windows Update
  3. Check for updates and install all pending security updates
  4. If the specific fixed build is not offered via Windows Update, verify that KBXXXXXX (the corresponding security patch) is installed
  5. Restart the system after updates are installed
  6. Confirm the build number matches or exceeds the fixed version: Windows 11 24h2 should be >=10.0.26100.6899, Windows 11 25h2 >=10.0.26200.6899, Windows Server 2022 23h2 >=10.0.25398.1913, Windows Server 2025 >10.0.26100.6899
Caveat Standard Windows update risks apply - ensure backups and test in staging environment before broad deployment; some updates may require restarts

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
  • 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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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-2025-59257 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