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Qsync CentralApplication · Qnap

CVE-2025-30261

MEDIUM · 6.5 CVSS v3.1 Published 2025-08-29
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
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
An allocation of resources without limits or throttling vulnerability has been reported to affect Qsync Central. If a remote attacker gains a user account, they can then exploit the vulnerability to prevent other systems, applications, or processes from accessing the same type of resource. We have already fixed the vulnerability in the following version: Qsync Central 5.0.0.0 ( 2025/06/13 ) and later

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 resource exhaustion vulnerability in Qsync Central where an attacker with valid user credentials can allocate resources without limits, causing denial of service for other legitimate users trying to access the same resources. The vulnerability allows a remote authenticated attacker to prevent systems, applications, or processes from accessing shared sync resources.

MitigationUpgrade Qsync Central to version 5.0.0.0 or later. If immediate patching is not feasible, implement account access controls and monitor for anomalous resource consumption patterns that may indicate exploitation.

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
Qsync CentralApplication
Affected:= 5.0.0.0

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
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 installed Qsync Central version
    Access the QNAP admin interface, go to App Center or Control Panel, locate Qsync Central, and note the version number displayed. Alternatively, access the QNAP device via SSH and run: cat /etc/config/qpkg.xml | grep -A5 Qsync or check the QPKG installation log.
    Affected if The installed version is exactly 5.0.0.0
  2. Confirm Qsync Central service is running
    Log into QNAP admin panel, check Control Panel > System Status > Services, or via SSH run: ps | grep -i qsync to verify the Qsync Central process is active.
    Affected if The service is running and the version is 5.0.0.0
  3. Verify Qsync Central web interface is accessible
    Attempt to access the Qsync Central web portal via browser at https://[QNAP-IP]/qsync or check if ports 8080/443 are listening: netstat -tlnp | grep -E '8080|443'
    Affected if The web interface responds and the backend version is 5.0.0.0
  4. Check for valid Qsync user accounts
    Review Qsync Central user list via the admin panel under Qsync Central > User Management, or query the system for active sync accounts.
    Affected if The system has active user accounts and Qsync Central version is 5.0.0.0

If Qsync Central version 5.0.0.0 is installed and the service is running with accessible user accounts, the environment is affected by this resource exhaustion vulnerability.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Qsync Central to version 5.0.0.0 or later. If immediate patching is not feasible, implement account access controls and monitor for anomalous resource consumption patterns that may indicate exploitation.

Recommended fix High confidence

Qsync Central 5.0.0.0 (2025/06/13) or later

  1. 1. Log in to the QNAP NAS administrative interface
  2. 2. Navigate to Qsync Central application settings
  3. 3. Check the current installed version of Qsync Central
  4. 4. If the version is earlier than the 2025/06/13 release of 5.0.0.0, proceed with update
  5. 5. Use App Center or the QNAP firmware update mechanism to update Qsync Central to the latest available version
  6. 6. Verify the update was successful by confirming the new version number

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

Fix this in Qsync Central Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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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-2025-30261 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