CVE-2021-38674Network attack vector

Browser code injection through TFTP Server XSS

Published Jan 7, 2022 · Updated Sep 16, 2024

Reflected XSS in TFTP Server in QNAP QTS, QuTS hero, and QuTScloud allows remote attackers to inject code into a user's browser. QNAP has not disclosed the affected request parameter or the exact operation that reflects untrusted input into the TFTP Server response. Exploitation requires user interaction; injected script executes in the affected page's browser context and can access or modify browser-accessible data without interrupting the service.

CVSS severity4.2
Medium
EPSS probability0.64%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in TFTP Server in QNAP QTS, QuTS hero, and QuTScloud allows remote attackers to inject code into a user's browser. QNAP has not disclosed the affected request parameter or the exact operation that reflects untrusted input into the TFTP Server response. Exploitation requires user interaction; injected script executes in the affected page's browser context and can access or modify browser-accessible data without interrupting the service.

The record

CVE
CVE-2021-38674
Published
Jan 7, 2022
Updated
Sep 16, 2024
Vendor
Linn Products Limited
Product
QuTS hero
Classifications
CWE-79, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 7, 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 <h4.5.4.1771 build 20210825

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Linn Products Limited · QuTS heroversion=unspecified <h4.5.4.1771 build 20210825
Linn Products Limited · QuTScloudversion=unspecified <c4.5.7.1864
Linn Products Limited · QTSversion=unspecified <4.5.4.1787 build 20210910

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.2QNAP Systems, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/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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