dbcve.org
Nas Proxy ServerApplication · Qnap

CVE-2021-34361

MEDIUM · 6.1 CVSS v3.1 Published 2022-02-25
Fix available
A fix is available. Upgrade to 1.4.2 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges

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 · high confidence

A stored cross-site scripting (XSS) vulnerability in QNAP Proxy Server allows remote attackers to inject malicious JavaScript or HTML into web requests processed by the proxy. The vulnerability stems from insufficient input validation in the Proxy Server component, which does not properly sanitize malicious payloads before rendering them in administrative interfaces or proxy-generated pages.

MitigationUpdate QNAP Proxy Server to version 1.4.2 or later for QTS 4.5.x systems. Prior to updating, backup proxy configurations and verify compatibility with existing network infrastructure.

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
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/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 Proxy Server is installed
    Log into the QNAP QTS administrative interface and navigate to App Center or use the command line (via SSH) to list installed applications. Look for 'Proxy Server' in the list of installed apps.
    Affected if Proxy Server is not found in the installed applications, the system is not affected by this specific vulnerability.
  2. Check Proxy Server version
    In QTS, go to App Center, find Proxy Server, and note the displayed version number. Alternatively, access Proxy Server settings through the admin panel and locate the version information.
    Affected if The installed version is any version prior to 1.4.2 (for example, 1.4.1, 1.4.0, or earlier).
  3. Confirm proxy service is enabled
    Access the QNAP Proxy Server settings via the QTS admin interface (typically under Network & Virtual Switch or Proxy settings) and verify that the proxy service is currently turned on or running.
    Affected if The proxy service is enabled and accessible over the network - this is required for the XSS payload to be processed and stored.
  4. Verify administrative interface accessibility
    Confirm that the QNAP admin interface and/or Proxy Server management pages are accessible (by default on ports 8080 or 443). Check network settings to see if the interface is exposed to untrusted networks.
    Affected if The administrative or proxy interface is exposed to remote attackers (not limited to localhost or trusted internal networks).

The environment is affected if QNAP Proxy Server is installed with a version earlier than 1.4.2 and the proxy service is 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 1.4.2 or later
Fixed in 1.4.2
Interim mitigation

Update QNAP Proxy Server to version 1.4.2 or later for QTS 4.5.x systems. Prior to updating, backup proxy configurations and verify compatibility with existing network infrastructure.

Recommended fix High confidence

Proxy Server 1.4.2 (QTS 4.5.x)

  1. 1. Log in to the QNAP device's QTS management interface
  2. 2. Navigate to the App Center or Proxy Server application
  3. 3. Check the current version of Proxy Server (verify it is below 1.4.2)
  4. 4. Update Proxy Server to version 1.4.2 or later
  5. 5. Verify the update was successful by checking the installed version

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

Fix this in Nas Proxy Server Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.

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-2021-34361 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