How severe is CVE-2021-28804?

CVE-2021-28804 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-28804 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-28804?

CVE-2021-28804 primarily affects Qnap Qts. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-28804?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-28804 published?

CVE-2021-28804 was published on 2021-07-01 and last updated on 2026-06-17.

CVE-2021-28804

CVE-2021-28804 is a critical-severity vulnerability in Qnap Qts with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-78.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-78
Affected product: Qnap Qts
Published: 2021-07-01
Last modified: 2026-06-17

Description

A command injection vulnerabilities have been reported to affect QTS and QuTS hero. If exploited, this vulnerability allows attackers to execute arbitrary commands in a compromised application. This issue affects: QNAP Systems Inc. QTS versions prior to 4.5.1.1540 build 20210107. QNAP Systems Inc. QuTS hero versions prior to h4.5.1.1582 build 20210217.

Frequently asked questions

What is CVE-2021-28804?: A command injection vulnerabilities have been reported to affect QTS and QuTS hero. If exploited, this vulnerability allows attackers to execute arbitrary commands in a compromised application. This issue affects: QNAP Systems Inc. QTS versions prior to 4.5.1.1540 build 20210107. QNAP Systems Inc. QuTS hero versions prior to h4.5.1.1582 build 20210217.
How severe is CVE-2021-28804?: CVE-2021-28804 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-28804 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-28804?: CVE-2021-28804 primarily affects Qnap Qts. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-28804?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-28804 published?: CVE-2021-28804 was published on 2021-07-01 and last updated on 2026-06-17.

References

https://www.qnap.com/zh-tw/security-advisory/qsa-21-29

Affected products (2)

cpe:2.3:o:qnap:qts:*:*:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:*:*:*:*:*:*:*:*

More vulnerabilities in Qnap Qts

CVE-2024-32766 — Critical (CVSS 10.0): An OS command injection vulnerability has been reported to affect several QNAP operating system versions. If exploited,…
CVE-2017-7876 — Critical (CVSS 10.0): This command injection vulnerability in QTS allows attackers to run arbitrary commands in the compromised application.…
CVE-2025-66276 — Critical (CVSS 9.8): QuTS hero is not affected. We have already fixed the vulnerability in the following version: QTS 5.2.7.3256 build…
CVE-2025-66277 — Critical (CVSS 9.8): A link following vulnerability has been reported to affect several QNAP operating system versions. The remote attackers…
CVE-2025-62849 — Critical (CVSS 9.8): An SQL injection vulnerability has been reported to affect several QNAP operating system versions. The remote attackers…
CVE-2025-59385 — Critical (CVSS 9.8): An authentication bypass by spoofing vulnerability has been reported to affect several QNAP operating system versions.…

All CVEs affecting Qnap Qts →

Other CWE-78 (OS Command Injection) vulnerabilities

CVE-2026-56004 — Critical (CVSS 10.0): A shellcode injection in the mercurial handler of the obs tar_scm source service before version 0.12.4 could be used by…
CVE-2026-56415 — Critical (CVSS 10.0): Storage Concentrator (SC & SCVM) contains a command injection vulnerability within the debug.pl script that is…
CVE-2026-56413 — Critical (CVSS 10.0): Storage Concentrator (SC & SCVM) contains a command injection vulnerability in the ms_service.pl service, which listens…
CVE-2026-49869 — Critical (CVSS 10.0): Kestra is an open-source, event-driven orchestration platform. Prior to 1.0.45 and 1.3.21, AuthenticationFilter in…
CVE-2026-49261 — Critical (CVSS 10.0): MariaDB server is a community developed fork of MySQL server. Versions 10.6.1 through 10.6.26, 10.11.1 through…
CVE-2026-10520 — Critical (CVSS 10.0): An OS Command Injection vulnerability in Ivanti Sentry before the R10.5.2, R10.6.2 and R10.7.1 versions allows a…

Browse all CWE-78 (OS Command Injection) vulnerabilities →