Threat Intelligence / CVE / CVE-2025-66281

CVE-2025-66281 — QNAP Systems Inc. QTS

CVSS v4.0 6.9 (Medium, derived from score) · EPSS 0.3% (higher than 25.0% of all scored CVEs) · Priority 4.5/10 · Published 2026-06-10

As of 2026-06-10, CVE-2025-66281 is a Medium-severity (band derived from the CVSS v4.0 score, not stated by the CNA) vulnerability in QNAP Systems Inc. QTS, CVSS v4.0 6.9, EPSS 0.3% (25.0th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2025-66281, most recently “QNAP QSA-26-10: Multiple Injection and Memory-Safety Vulnerabilities in QTS, QuTS hero, QuTS cloud, QVP, and File Station (CVE-2025-66273, CVE-2026-26240, and 12 others)”.

Last updated: 2026-06-10

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 94 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

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 .

Other references

Full detection coverage & IOCs for threats exploiting CVE-2025-66281 are available via the Threadlinqs MCP server (Purple tier). View plans →

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