Cyber Resilience

CVE-2020-2509

RCE in Qnap Qts ≤ 4.2.6

CISA KEVActive ExploitationEUVD ExploitedRCECommand Injection
Published
17 April 2021
Modified
27 October 2025
KEV Added
11 April 2022
Patch / advisory
CVSS Score v3.1 9.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.33 98th percentile
Risk Priority 97 floored blend · peak EPSS

Summary

CVE-2020-2509 is a critical-severity Command Injection (CWE-77) vulnerability in Qnap Qts. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Command and Scripting Interpreter (T1059); ranked in the top 2% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2020-2509 is a command injection vulnerability affecting QNAP QTS and QuTS hero network-attached storage operating systems. The flaw, tracked under CWE-77 and CWE-78, permits improper neutralization of special elements used in commands and carries a CVSS v3.1 base score of 9.8 reflecting network attack vector, low complexity, and no required privileges or user interaction.

Unauthenticated remote attackers can exploit the issue to execute arbitrary commands inside the compromised application, resulting in impacts to confidentiality, integrity, and availability.

QNAP's security advisory QSA-21-05 states that the vulnerability has been fixed in 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, and QuTS hero h4.5.1.1491 build 20201119 and later.

The CVE is listed in the CISA known exploited vulnerabilities catalog, confirming observed real-world exploitation.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

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…

more

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

CWE(s)
KEV Date Added
11 April 2022

Related Threats

MITRE ATT&CK Enterprise Techniques

T1059 Command and Scripting Interpreter Execution
Adversaries may abuse command and script interpreters to execute commands, scripts, or binaries.
T1059.003 Windows Command Shell Execution
Adversaries may abuse the Windows command shell for execution.
T1059.004 Unix Shell Execution
Adversaries may abuse Unix shell commands and scripts for execution.
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
T1059.001 PowerShell Execution
Adversaries may abuse PowerShell commands and scripts for execution.
T1059.008 Network Device CLI Execution
Adversaries may abuse scripting or built-in command line interpreters (CLI) on network devices to execute malicious command and payloads.
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-22481Same product: Qnap Qts
CVE-2024-53692Same product: Qnap Qts
CVE-2024-21903Same product: Qnap Qts
CVE-2025-30264Same product: Qnap Qts
CVE-2024-38641Same product: Qnap Qts
CVE-2018-19949Same product: Qnap Qtsboth on KEV
CVE-2023-41281Same product: Qnap Qts
CVE-2023-41283Same product: Qnap Qts
CVE-2023-45025Same product: Qnap Qts
CVE-2023-41282Same product: Qnap Qts

Affected Assets

qnap
qts
4.2.6, 4.3.3.0174, 4.3.3.0868, 4.3.3.0998, 4.3.3.1051 · ≤ 4.2.6 · 4.3.5 — 4.3.6 · 4.4.0 — 4.5.1
qnap
quts hero
h4.5.1, h4.5.1.1472 · ≤ h4.5.1

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

Detect
Catch it (NIST detect / respond)

Harden
Shrink the surface (DISA STIG)

Validate
Prove the fix (OWASP ASVS)
  • V1.2.3
  • V1.2.5
  • V1.2.8
  • V1.2.9

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

addresses: CWE-78

Platform-independent apps typically execute inside a managed runtime or sandbox that restricts direct OS command execution, reducing the ability to exploit OS command injection.

addresses: CWE-78

Validates inputs to block special elements that would alter OS command execution.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly require input validation and neutralization that prevent command injection.

DE.CM-09 partial match
prevents

Runtime monitoring of software and data can detect anomalous command execution resulting from injection.

ID.RA-01 partial match
prevents

Identifying recorded vulnerabilities enables remediation of command-injection flaws before exploitation.

PR.PS-02 partial match
prevents

Routine patching/maintenance can remediate known command-injection CVEs in dependencies (partial forward) but does nothing to stop developers from introducing improper neutralization in custom code (none reverse).

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

prevents

Secure coding standards require proper escaping and parameterization of commands, directly eliminating CWE-77.

finds

Security testing in development catches command-injection vulnerabilities before release.

prevents

Secure development life cycle mandates input validation and command construction practices that directly prevent command injection.

prevents

Application security requirements explicitly call for controls against injection flaws including command injection.

prevents

Secure architecture principles reduce the attack surface but do not prescribe the specific neutralization techniques needed.

none

Environment separation limits the blast radius of an exploited command injection but does not prevent the flaw itself.

References