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Azure File SyncApplication · Microsoft

CVE-2025-53729

HIGH · 7.8 CVSS v3.1 Published 2025-08-12
Fix available
A fix is available. Upgrade to 18.3.0.0 / 19.2.0.0 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
Improper access control in Azure File Sync 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

Azure File Sync contains an improper access control vulnerability that allows an already-authorized attacker to escalate their privileges locally on the affected system. This is a local privilege elevation issue stemming from insufficient access control enforcement in the Azure File Sync component.

MitigationApply Microsoft security updates for Azure File Sync when released. Review and restrict local user permissions to the principle of least privilege as an interim measure.

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
Azure File SyncApplication
Affected:>= 18.0.0.0, < 18.3.0.0>= 19.0.0.0, < 19.2.0.0>= 20.0.0.0, < 20.1.0.0>= 21.0.0.0, <= 21.1.0.0

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. Verify Azure File Sync is installed
    Check for the Azure File Sync service named 'FileSyncSvc' in Services.msc, or look for installation in Program Files\Azure\FileSync, or check registry key HKLM\SOFTWARE\Microsoft\Azure\FileSync
    Affected if Azure File Sync is not installed on the system
  2. Find installed Azure File Sync version
    Right-click the executable StorageSyncServiceHost.exe in the Azure File Sync installation folder (typically Program Files\Azure\FileSync\Agent), select Properties, and view the File Version; or run: (Get-ItemProperty -Path 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*' | Where-Object {$_.DisplayName -like '*Azure File Sync*'}).DisplayVersion
    Affected if No version is returned or Azure File Sync is not found
  3. Compare version against affected ranges
    Compare the installed version number to these ranges: 18.0.0.0 through 18.2.x.x, 19.0.0.0 through 19.1.x.x, 20.0.0.0 through 20.0.x.x, 21.0.0.0 through 21.1.0.0
    Affected if The installed version falls within any of these ranges (18.0.0.0 to <18.3.0.0, 19.0.0.0 to <19.2.0.0, 20.0.0.0 to <20.1.0.0, or 21.0.0.0 to <=21.1.0.0)
  4. Confirm local user environment
    Run 'Get-LocalUser' in PowerShell to list local user accounts on the system
    Affected if Multiple local user accounts exist and Azure File Sync is running under a service account with elevated local permissions that could be exploited for privilege escalation

The system is affected if Azure File Sync is installed with a version matching any of the four affected ranges and the service runs with elevated local permissions accessible to other local users.

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 18.3.0.0 / 19.2.0.0 / 20.1.0.0 or later
Fixed in 18.3.0.019.2.0.020.1.0.0
Interim mitigation

Apply Microsoft security updates for Azure File Sync when released. Review and restrict local user permissions to the principle of least privilege as an interim measure.

Recommended fix High confidence

Upgrade to version 18.3.0.0 or later for 18.x branch; 19.2.0.0 or later for 19.x branch; 20.1.0.0 or later for 20.x branch; 21.2.0.0 or latest 21.x for 21.x branch

  1. Identify the currently installed Azure File Sync version using Get-StorageSyncServer or the Storage Sync service properties in Azure portal
  2. Determine which version branch (18.x, 19.x, 20.x, or 21.x) you are currently running
  3. For Azure File Sync agents running on Windows servers, download the latest agent from the Microsoft Update Catalog or Microsoft Download Center
  4. Follow the standard Azure File Sync agent upgrade procedure: stop the Azure File Sync service (Stop-Service -Name 'FileSyncSvc'), run the installer for the fixed version, restart the service
  5. Alternatively, for agent updates managed through Azure, navigate to the Storage Sync Service in the Azure portal, select 'Sync groups', choose the relevant server, and apply the update
  6. After upgrading, verify the new version using Get-StorageSyncServer to confirm it matches or exceeds 18.3.0.0, 19.2.0.0, 20.1.0.0, or 21.2.0.0 respectively
  7. Test that file synchronization continues to function correctly after the upgrade
Caveat Review Azure File Sync release notes before upgrading; minor agent updates typically do not introduce breaking changes but always test in a non-production environment first

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

Fix this in Azure File Sync Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

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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-2025-53729 in production — separate from our analysis above.

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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