CVE-2021-34361Network attack vector

Browser code execution via undisclosed XSS flaw

Published Feb 25, 2022 · Updated Sep 16, 2024

Cross-site scripting in QNAP Proxy Server before 1.4.2 allows remote attackers to execute malicious code in a user's browser. QNAP has not disclosed the affected request parameter, rendering locus, or missing input-neutralization operation. Exploitation requires user interaction; the published assessment identifies browser-side confidentiality loss without integrity or availability impact.

CVSS severity5.3
Medium
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in QNAP Proxy Server before 1.4.2 allows remote attackers to execute malicious code in a user's browser. QNAP has not disclosed the affected request parameter, rendering locus, or missing input-neutralization operation. Exploitation requires user interaction; the published assessment identifies browser-side confidentiality loss without integrity or availability impact.

The record

CVE
CVE-2021-34361
Published
Feb 25, 2022
Updated
Sep 16, 2024
Vendor
Linn Products Limited
Product
Proxy Server
Classifications
CWE-79, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 25, 2022CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <1.4.2 ( 2021/12/30 )

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Linn Products Limited · Proxy Serverversion=unspecified <1.4.2 ( 2021/12/30 )

Published CVSS scores

5.3QNAP Systems, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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