dbcve.org
Nas Proxy ServerApplication · Qnap

CVE-2021-34359

MEDIUM · 5.4 CVSS v3.1 Published 2022-02-25
Fix available
A fix is available. Upgrade to 1.4.2 or later.
See remediation →
58/100
Remediation priority · Elevated
Remotely reachable

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 cross-site scripting (XSS) vulnerability has been reported to affect QNAP device running Proxy Server. If exploited, this vulnerability allows remote attackers to inject malicious code. We have already fixed this vulnerability in the following versions of Proxy Server: QTS 4.5.x: Proxy Server 1.4.2 ( 2021/12/30 ) 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 cross-site scripting (XSS) vulnerability exists in QNAP Proxy Server that allows remote attackers to inject malicious JavaScript or HTML code into web pages served by the proxy. The vulnerability is exploitable remotely without authentication, likely through unsanitized user input being reflected in HTTP responses.

MitigationUpgrade QNAP Proxy Server to version 1.4.2 or later (released 2021/12/30) for QTS 4.5.x systems. Until patched, consider disabling the Proxy Server or restricting network access to trusted users.

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
Nas Proxy ServerApplication
Affected:< 1.4.2

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
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/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 QNAP Proxy Server is installed
    Log into QTS admin console and navigate to App Center or Control Panel > Applications > Proxy Server to confirm the Proxy Server app is installed.
    Affected if Proxy Server app is present on the QNAP system
  2. Check Proxy Server version
    In QTS, go to the Proxy Server application settings or App Center and locate the installed version number. Compare it against the vulnerable version threshold of 1.4.2.
    Affected if Installed version is lower than 1.4.2
  3. Confirm Proxy Server is enabled and running
    Access the Proxy Server status page in QTS or use the QNAP admin interface to verify the service status shows as running and the proxy service is actively serving requests.
    Affected if Proxy Server is running and accessible via network
  4. Verify network exposure
    Check if the proxy service port (default HTTP 8080 or configured port) is exposed to untrusted networks by reviewing Firewall rules or port forwarding settings in QTS Control Panel.
    Affected if Proxy Server port is accessible from untrusted networks or the internet
  5. Inspect HTTP response headers
    Send a test request to the proxy server with a crafted URL parameter (such as ?test=<script>alert(1)</script>) and capture the response. Examine if the input is reflected without sanitization in the HTTP response body or headers.
    Affected if Input is reflected unsanitized in proxy responses

A QNAP system is affected if Proxy Server is installed with a version below 1.4.2 and the service is running 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 1.4.2 or later
Fixed in 1.4.2
Interim mitigation

Upgrade QNAP Proxy Server to version 1.4.2 or later (released 2021/12/30) for QTS 4.5.x systems. Until patched, consider disabling the Proxy Server or restricting network access to trusted users.

Recommended fix High confidence

Proxy Server 1.4.2 (QTS 4.5.x)

  1. Log in to the QNAP NAS admin interface (QTS)
  2. Navigate to App Center or the application management section
  3. Locate 'Proxy Server' in the installed applications
  4. Check the current version to confirm it is below 1.4.2
  5. Select Proxy Server and click Update or Install Update
  6. Wait for the update to complete to version 1.4.2 or later
  7. Verify the installation was successful and the new version is 1.4.2 or later

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

Fix this in Nas Proxy Server 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-2021-34359 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