CVE-2025-66281: A NULL pointer dereference vulnerability has been reported to affect several QNAP operating system versions

Q: How do I fix CVE-2025-66281?

qts: upgrade to 5.2.9.3410; quts hero: upgrade to h5.2.9.3410, h5.3.4.3500, h6.0.0.3397. Exact commands for each OS are on this page.

Q: Is CVE-2025-66281 being exploited?

CVE-2025-66281 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2025-66281 affect?

CVE-2025-66281 affects qts, quts hero. Severity is high (CVSS 7.2). A NULL pointer dereference vulnerability has been reported to affect several QNAP operating system versions. The remote attackers can then exploit the vulnerability to launch a denial-of-service (DoS) attack. We have already fixed the vuln

Routine

HIGH 7.2UPGRADEUPGRADE

CVE-2025-66281 is a high-severity flaw (CVSS 7.2) affecting qts, quts hero. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A NULL pointer dereference vulnerability has been reported to affect several QNAP operating system versions. The remote attackers can then exploit the vulnerability to launch a denial-of-service (DoS) attack. We have already fixed the vulnerability in the following versions: QTS 5.2.9.3410 build 20260214 and later QuTS hero h5.2.9.3410 build 20260214 and later QuTS hero h5.3.4.3500 build 20260520 and later QuTS hero h6.0.0.3397 build 20260206 an

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	7.2 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	None
EPSS exploit chance	0.5% (top 61%)
CISA exploited list	No
Weakness	CWE-476
Published	2026-06-10
Last modified	2026-07-23

Publisher (CNA): QNAP Systems, Inc. · Vendor: qnap

Last updated 2026-07-23 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-10 04:17 UTCPublished CVE record published
2026-07-23 09:10 UTCUpdated Record last modified

qnap qts UPGRADE

Affected: >= 5.2.0.2737 and < 5.2.9.3410

Fixed in: 5.2.9.3410

Safe to downgrade to: a release before 5.2.0.2737

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

qnap quts hero UPGRADE

Affected: >= h5.2.0.2737 and < h5.2.9.3410 · >= h5.3.0.3115 and < h5.3.4.3500 · >= h6.0.0.3324 and < h6.0.0.3397

Fixed in: h5.2.9.3410, h5.3.4.3500, h6.0.0.3397

Safe to downgrade to: a release before h5.2.0.2737

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2025-66281?

qts: upgrade to 5.2.9.3410; quts hero: upgrade to h5.2.9.3410, h5.3.4.3500, h6.0.0.3397. Exact commands for each OS are on this page.

Is CVE-2025-66281 being exploited?

CVE-2025-66281 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2025-66281 affect?

CVE-2025-66281 affects qts, quts hero. Severity is high (CVSS 7.2). A NULL pointer dereference vulnerability has been reported to affect several QNAP operating system versions. The remote attackers can then exploit the vulnerability to launch a denial-of-service (DoS) attack. We have already fixed the vuln

How urgent is CVE-2025-66281?

Priority 35/100. High severity

Software pages

QNAP vulnerabilities

Related CVEs

CVE-2025-66276 CRITICAL 9.8 UPGRADE QuTS hero is not affected. We have already fixed the vulnerability in the following version: QTS 5.2.7.3256 b
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References

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