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PatchSiren cyber security CVE debrief

CVE-2025-66281 QNAP CVE debrief

CVE-2025-66281 is a NULL pointer dereference vulnerability reported in several QNAP operating system versions. This vulnerability allows remote attackers to launch a denial-of-service (DoS) attack. The vulnerability has been fixed 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, and QuTS hero h6.0.0.3397 build 20260206 and later.

Vendor
QNAP
Product
QTS
CVSS
MEDIUM 6.9
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-10
Original CVE updated
2026-06-10
Advisory published
2026-06-10
Advisory updated
2026-06-10

Who should care

Users of affected QNAP operating system versions should update to the fixed versions to prevent exploitation.

Technical summary

The vulnerability is a NULL pointer dereference, which can be exploited to launch a denial-of-service (DoS) attack. The CVSS score is 6.9, and the severity is MEDIUM.

Defensive priority

MEDIUM

Recommended defensive actions

  • Update to QTS 5.2.9.3410 build 20260214 or later
  • Update to QuTS hero h5.2.9.3410 build 20260214 or later
  • Update to QuTS hero h5.3.4.3500 build 20260520 or later
  • Update to QuTS hero h6.0.0.3397 build 20260206 or later

Evidence notes

The vulnerability was reported by an unknown vendor, but evidence suggests that QNAP is the affected vendor.

Official resources

CVE-2025-66281 was published on 2026-06-10T04:17:14.383Z and modified on 2026-06-10T19:43:28.857Z.