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Qsync CentralApplication · Qnap

CVE-2025-30266

MEDIUM · 6.5 CVSS v3.1 Published 2026-02-11
Fix available
A fix is available. Upgrade to 5.0.0.4 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
A NULL pointer dereference vulnerability has been reported to affect Qsync Central. If a remote attacker gains a user account, they can then exploit the vulnerability to launch a denial-of-service (DoS) attack. We have already fixed the vulnerability in the following version: Qsync Central 5.0.0.4 ( 2026/01/20 ) 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

A NULL pointer dereference vulnerability in Qsync Central allows an authenticated remote attacker to cause a denial-of-service condition. The attacker must first obtain valid user credentials before exploiting the vulnerability.

MitigationUpdate Qsync Central to version 5.0.0.4 or later. Implement strict access controls and strong password policies to prevent unauthorized account creation that could enable 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, < 5.0.0.4

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 Qsync Central version
    Access the Qsync Central admin interface and navigate to the Control Panel or About section to view the installed software version. Alternatively, check the version via the QNAP NAS firmware or app management interface.
    Affected if The displayed version is 5.0.0.0, 5.0.0.1, 5.0.0.2, or 5.0.0.3 (any version >= 5.0.0.0 but < 5.0.0.4).
  2. Confirm Qsync Central service is running
    Log into the QNAP NAS admin interface and verify that the Qsync Central application is installed and currently running. Check the App Center or Services status for Qsync Central.
    Affected if Qsync Central is installed and running on the system.
  3. Verify user authentication is enabled
    Access the Qsync Central settings and confirm that user authentication is configured. Check the User Management or Access Control settings to ensure users require login credentials to access Qsync features.
    Affected if User authentication is enabled and user accounts exist in the system.
  4. Assess network accessibility
    Determine if the Qsync Central web interface is exposed to network access. Check the NAS network settings, firewall rules, or myQNAPcloud configuration to see if port 8080 (or the configured Qsync port) is accessible from untrusted networks.
    Affected if The Qsync Central interface is reachable from networks outside the trusted local environment.

You are affected if Qsync Central version is between 5.0.0.0 and 5.0.0.3 inclusive, the service is running, user authentication is configured, and the service is network-accessible to potential attackers.

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 5.0.0.4 or later
Fixed in 5.0.0.4
Interim mitigation

Update Qsync Central to version 5.0.0.4 or later. Implement strict access controls and strong password policies to prevent unauthorized account creation that could enable exploitation.

Recommended fix High confidence

Qsync Central 5.0.0.4

  1. 1. Check the current version of Qsync Central installed on your QNAP NAS via the QNAP Control Panel or App Center.
  2. 2. Navigate to the QNAP download center at www.qnap.com/en/support-download.php to download Qsync Central version 5.0.0.4 or later.
  3. 3. Install the updated Qsync Central application on your QNAP NAS.
  4. 4. Restart the Qsync Central service if not automatically restarted after the update.
  5. 5. Verify the installed version is 5.0.0.4 or higher to confirm the vulnerability is patched.

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
  • Implementation1.0 h
  • Testing3.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,210
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,936.

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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-2025-30266 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