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Qsync CentralApplication · Qnap

CVE-2025-30263

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

MitigationUpgrade Qsync Central to version 5.0.0.0 (released 2025/06/13) or later. Additionally, limit user account access and monitor for suspicious authentication activity.

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. Verify Qsync Central is installed
    Check if the Qsync Central service exists on the QNAP device. This is typically found in the QNAP App Center or via command line: ls -la /share/CACHEDEV1_DATA/.qpkg/QSync/ or checking the QNAP firmware interface.
    Affected if Qsync Central is not installed on the device, the vulnerability does not apply.
  2. Determine installed Qsync Central version
    Access QNAP Admin Console > Apps > Qsync Central > Settings, or check via SSH using: cat /share/CACHEDEV1_DATA/.qpkg/QSync/package.ini | grep Version
    Affected if The installed version is earlier than 5.0.0.0 (the patched release date is 2025/06/13). Compare your version against this baseline.
  3. Confirm remote access is enabled
    Check if Qsync Central is configured to accept remote connections. In QNAP admin: Qsync Central > Settings > General > enable 'Allow remote access' or check /etc/config/qsync/qsync.conf for remote access settings.
    Affected if Remote access is disabled and no external users can authenticate, exploitation is not possible.
  4. Review authentication configuration
    Examine user account settings in Qsync Central: Qsync Central > Settings > User Management. Verify which local or domain users have access to Qsync Central.
    Affected if No valid user accounts exist in Qsync Central, the attacker cannot authenticate to exploit the NULL pointer dereference.
  5. Check system logs for crashes or instability
    Review QNAP system logs in Admin Console > System Logs > Application Logs, or via SSH: cat /var/log/qsync.log. Look for NULL pointer, segmentation fault, or service restart entries.
    Affected if Qsync Central service has crashed or restarted unexpectedly, this may indicate the vulnerability has been triggered.

You are affected if Qsync Central is installed with a version earlier than 5.0.0.0, remote access is enabled, and valid user accounts exist in the system.

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 (released 2025/06/13) or later. Additionally, limit user account access and monitor for suspicious authentication activity.

Recommended fix High confidence

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

  1. 1. Check the current version of Qsync Central installed on your system
  2. 2. If the installed version is older than Qsync Central 5.0.0.0 (2025/06/13), obtain and install the updated version from the QNAP website or through the QNAP Control Center
  3. 3. After upgrade, verify the installed version is 5.0.0.0 (2025/06/13) or later
  4. 4. Confirm Qsync Central is functioning normally after the update

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
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
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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-2025-30263 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