CVE-2021-28816Network attack vector

Authenticated code execution via undisclosed stack overflow

Published Sep 10, 2021 · Updated Sep 17, 2024

Stack buffer overflow in QNAP QTS, QuTScloud, and QuTS hero allows remote authenticated users to execute arbitrary code over the network. QNAP has not disclosed the affected component, input path, or operation that writes beyond the stack buffer. Reaching the flaw requires low-privileged authentication; successful exploitation runs code in the vulnerable service's context.

CVSS severity7.6
High
EPSS probability0.93%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack buffer overflow in QNAP QTS, QuTScloud, and QuTS hero allows remote authenticated users to execute arbitrary code over the network. QNAP has not disclosed the affected component, input path, or operation that writes beyond the stack buffer. Reaching the flaw requires low-privileged authentication; successful exploitation runs code in the vulnerable service's context.

The record

CVE
CVE-2021-28816
Published
Sep 10, 2021
Updated
Sep 17, 2024
Vendor
Linn Products Limited
Product
QuTS hero
Classifications
CWE-787, T1210
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 10, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 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 privilegesauthenticated

What is affected?

Linn Products Limited · QuTS heroversion=unspecified <h4.5.4.1771 build 20210825
Linn Products Limited · QuTScloudversion=unspecified <c4.5.6.1755
Linn Products Limited · QTSversion=unspecified <4.3.3.1693 build 20210624; version=unspecified <4.3.6.1750 build 20210730; version=unspecified <4.5.4.1715 build 20210630; version=unspecified <5.0.0.1716 build 20210701

Published CVSS scores

7.6QNAP Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1210Exploitation of Remote Services

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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