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Exploited. On CISA's list since 2022-04-11.
CVE-2020-2509 · QNAP QNAP Network-Attached Storage (NAS) · Published 2021-04-17
9.8 out of 10
CVSS rates it critical: about as damaging as flaws get.
34%
Estimated chance of exploitation in the next 30 days, higher than 98% of all scored flaws (EPSS, 2026-10-29).
Yes
CISA has seen it exploited in real attacks. For US government agencies the fix is deadline passed 1642 days ago (2022-05-02).
Apply updates per vendor instructions.
QNAP NAS devices contain a command injection vulnerability which could allow attackers to perform remote code execution.
A command injection vulnerability has been reported to affect QTS and QuTS hero. If exploited, this vulnerability allows attackers to execute arbitrary commands in a compromised application. We have already fixed this vulnerability in the following versions: QTS 4.5.2.1566 Build 20210202 and later QTS 4.5.1.1495 Build 20201123 and later QTS 4.3.6.1620 Build 20210322 and later QTS 4.3.4.1632 Build 20210324 and later QTS 4.3.3.1624 Build 20210416 and later QTS 4.2.6 Build 20210327 and later QuTS hero h4.5.1.1491 build 20201119 and later
From the NVD.
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Understand the kind of weakness behind this flaw. These resources teach the weakness, rather than reproduce this specific CVE. Follow the vendor's advice above to fix the affected product.
Input changes a command that the server runs through its operating system.
CWE-78 · CISA KEV; NVD record: security@qnapsecurity.com.tw
Reading and practice labs · Free account for labs. Basic HTTP knowledge; some labs use Burp Suite.
CWE-77 · CISA KEV; NVD record: nvd@nist.gov; NVD record: security@qnapsecurity.com.tw. We have not selected a close learning match for this label.
CWE is a catalogue of weakness types. Labels come from the sources shown and can differ or change. Resource matches reviewed 16 October 2026.
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Exploited flaws from CISA's KEV catalogue. Chance of exploitation from EPSS by FIRST. Descriptions and scores from the NVD. This product uses the NVD API but is not endorsed or certified by the NVD.