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QtsOperating system · Qnap

CVE-2017-17027

CRITICAL · 9.8 CVSS v3.0 Published 2017-12-21
Fix available
A fix is available. Upgrade to after 4.3.3.0378 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges 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 buffer overflow vulnerability in FTP service in QNAP QTS version 4.2.6 build 20171026, 4.3.3.0378 build 20171117, 4.3.4.0387 (Beta 2) build 20171116 and earlier could allow remote attackers to execute arbitrary code on NAS devices.

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

Buffer overflow vulnerability in the FTP service of QNAP QTS firmware allows remote attackers to execute arbitrary code by sending malformed FTP commands that overflow a buffer, potentially giving them full control of the NAS device.

MitigationUpdate QNAP QTS firmware to a version newer than the affected builds. If immediate patching is not possible, disable the FTP service and ensure the NAS is not directly exposed to the internet.

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
QtsOperating system
Affected:<= 4.3.3.0378= 4.3.4.0358= 4.3.4.0370= 4.3.4.0372= 4.3.4.0374= 4.3.4.0387

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
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/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. Confirm the device is a QNAP NAS running QTS
    Access the QTS admin console (typically via web browser to the device IP) and check the system information page, or run 'get_system_info' via QNAP CLI if available.
    Affected if The device is not a QNAP NAS or does not run QTS firmware.
  2. Identify the installed QTS firmware version
    In QTS admin panel, go to Control Panel > System > Firmware Update > Firmware Information, or check the version displayed on the login page. The version will be in format like 4.3.x.xxxx.
    Affected if The firmware version is <= 4.3.3.0378, or exactly 4.3.4.0358, 4.3.4.0370, 4.3.4.0372, 4.3.4.0374, or 4.3.4.0387.
  3. Verify the FTP service is enabled
    In QTS admin panel, go to Control Panel > Applications > FTP Service, or check via QNAP CLI with 'services.sh status' to see if the FTP daemon is running.
    Affected if The FTP service is currently enabled and running on the NAS.
  4. Check FTP network accessibility
    Determine if the NAS FTP port (21/TCP) is exposed to untrusted networks by reviewing firewall rules, router port forwarding settings, or by running a port scan from an external location.
    Affected if Port 21/TCP is accessible from the internet or untrusted networks.

A user is affected if they operate a QNAP NAS running QTS within the specified version range AND have the FTP service enabled and accessible.

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 a release after 4.3.3.0378
Interim mitigation

Update QNAP QTS firmware to a version newer than the affected builds. If immediate patching is not possible, disable the FTP service and ensure the NAS is not directly exposed to the internet.

Recommended fix High confidence

QTS version 4.3.4.0387 or later stable release

  1. Log into QNAP QTS as an administrator
  2. Navigate to Control Panel > System > Firmware Update
  3. Check for available updates and ensure the system updates to QTS version 4.3.4.0387 or later
  4. If automatic updates are not available, manually download the firmware from the official QNAP download center and update via Control Panel > System > Firmware Update > Manual Firmware Update
  5. After updating, verify the QTS version in Control Panel > System > Firmware Update to confirm the fix is applied
  6. Ensure the FTP service is re-enabled if it was disabled as a temporary mitigation
Caveat Review QNAP release notes for version 4.3.4.0387+ to check for any functionality changes or known issues before upgrading

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

Fix this in Qts Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
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Scan for this in your stack

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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-2017-17027 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