What is CVE-2021-28804?

CVE-2021-28804 is a critical-severity vulnerability in QNAP Qts, classified under OS Command Injection. CVSS score: 9.8/10. Published 2021-07-01.

How severe is CVE-2021-28804?

Critical severity. CVSS v3 base score is 9.8 out of 10.

RCE in QNAP Qts

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.

Vulnerability class: Command Injection (OS Command Injection)

Published 2021-07-01 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.018 (77.8th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 78th percentile — 77.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.018 · newest: 0.018 · change: 0.000

Affected products

QNAP Qts
QNAP Quts Hero
QNAP Systems Inc. Qts — versions unspecified
QNAP Systems Inc. Quts Hero — versions unspecified

Weakness classification (CWE)

CWE-78 — OS Command Injection

References

www.qnap.com/zh-tw/security-advisory/qsa-21-29 (Vendor Advisory)

Frequently asked questions

What is CVE-2021-28804?: CVE-2021-28804 is a critical-severity vulnerability in QNAP Qts, classified under OS Command Injection. CVSS score: 9.8/10. Published 2021-07-01.
How severe is CVE-2021-28804?: Critical severity. CVSS v3 base score is 9.8 out of 10.