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Qsync CentralApplication · Qnap

CVE-2025-30269

HIGH · 8.1 CVSS v3.1 Published 2026-02-11
Fix available
A fix is available. Upgrade to 5.0.0.4 or later.
See remediation →
87/100
Remediation priority · High
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 use of externally-controlled format string vulnerability has been reported to affect Qsync Central. If a remote attacker gains a user account, they can then exploit the vulnerability to obtain secret data or modify memory. 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 · high confidence

A format string vulnerability in Qsync Central allows authenticated users to inject format specifiers into formatted string functions. Since the format string is externally controlled, an attacker can use %s, %x, %n and similar specifiers to read data from the stack (potentially exposing secrets) or write to arbitrary memory locations.

MitigationUpdate Qsync Central to version 5.0.0.4 or later. Until patched, limit access to only trusted, verified user accounts since the vulnerability requires a valid user credential.

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
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

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
    Log into the QNAP NAS web interface and check the installed apps, or use the QNAP command line to list installed packages (e.g., 'qpkg --status' or check /share/CACHEDEV1_DATA/.qpkg/).
    Affected if Qsync Central is not present on the system, the vulnerability does not apply.
  2. Locate the Qsync Central version
    In the QNAP web interface, go to App Center > Qsync Central and view the version information, or use the command line 'qpkg --info Qsync_Central' if available.
    Affected if Unable to retrieve version information indicates Qsync Central may not be properly installed.
  3. Compare installed version against affected range
    Check if the installed version falls within >= 5.0.0.0 and < 5.0.0.4. Note that versions 5.0.0.0 through 5.0.0.3 are affected.
    Affected if The system is affected if Qsync Central version is 5.0.0.0, 5.0.0.1, 5.0.0.2, or 5.0.0.3.
  4. Confirm the Qsync Central service is running
    Check if the Qsync Central service is active via the QNAP interface or by verifying the process is running (e.g., 'ps' command on the NAS).
    Affected if The vulnerability is only exploitable when the Qsync Central service is actively running.

A system is affected by CVE-2025-30269 if Qsync Central is installed, the service is running, and the installed 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).

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. Until patched, limit access to only trusted, verified user accounts since the vulnerability requires a valid user credential.

Recommended fix High confidence

Qsync Central 5.0.0.4

  1. 1. Back up current Qsync Central configuration and data before proceeding with the update.
  2. 2. Download Qsync Central version 5.0.0.4 or later from the official QNAP download center (www.qnap.com).
  3. 3. Access the QNAP admin console and navigate to the Qsync Central application management area.
  4. 4. Install or update Qsync Central to version 5.0.0.4 or later.
  5. 5. After the update completes, verify the installed version matches 5.0.0.4 or higher.
  6. 6. Test that Qsync Central functionality is operating normally after the upgrade.

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

Fix this in Qsync Central Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,640
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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-2025-30269 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