What is CVE-2025-66281?
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 and later
The record classifies CVE-2025-66281 under weakness class CWE-476. 2 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 140 days ago.
Severity and exploitation probability
- CVSS v4.0 base score
- 6.9 — Medium (derived from score)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N - EPSS (FIRST)
- 0.3% probability of exploitation in the next 30 days, higher than 25.0% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 4.5/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-06-10
Is CVE-2025-66281 being exploited?
No public exploitation evidence for CVE-2025-66281 is recorded in the sources Threadlinqs tracks — CISA KEV, Exploit-DB, public proof-of-concept repositories and ProjectDiscovery Nuclei — as of 2026-06-10. That is an absence of evidence in those feeds, not a guarantee that the vulnerability is unexploited.
Affected products and versions
- QNAP Systems Inc.: QTS, QuTS hero
How to fix CVE-2025-66281
No vendor patch reference has been recorded for CVE-2025-66281 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.
Threat activity tracking CVE-2025-66281
1 tracked threat in the Threadlinqs corpus references CVE-2025-66281, either in the campaign’s CVE list or as an indicator on the campaign record.
Sources
Enriched from CVE.org, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on .