CVE-2025-66281Network attack vector

Pre-authentication service interruption via missing Content-Length

Published Jun 10, 2026 · Updated Jun 10, 2026

NULL pointer dereference in QNAP QTS and QuTS hero allows remote attackers to interrupt NAS services with a malformed HTTP request. A pre-authentication HTTP handler dereferences a NULL pointer when the Content-Length header is missing or empty, terminating the affected process. No credentials or user interaction are required; the published impact is limited to a service interrupt, with no reported data access or modification.

CVSS severity6.9
Medium
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

NULL pointer dereference in QNAP QTS and QuTS hero allows remote attackers to interrupt NAS services with a malformed HTTP request. A pre-authentication HTTP handler dereferences a NULL pointer when the Content-Length header is missing or empty, terminating the affected process. No credentials or user interaction are required; the published impact is limited to a service interrupt, with no reported data access or modification.

The record

CVE
CVE-2025-66281
Published
Jun 10, 2026
Updated
Jun 10, 2026
Vendor
Linn Products Limited
Product
QuTS hero
Classifications
CWE-476, CAPEC-129, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=h5.2.0 <h5.2.9.3410 build 20260214
  2. Affected versionversion=h5.3.0 <h5.3.4.3500 build 20260520
  3. Affected versionversion=? <h6.0.0.3397 build 20260206

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Linn Products Limited · QuTS heroversion=h5.2.0 <h5.2.9.3410 build 20260214; version=h5.3.0 <h5.3.4.3500 build 20260520; version=? <h6.0.0.3397 build 20260206
Linn Products Limited · QTSversion=5.2.0 <5.2.9.3410 build 20260214

Published CVSS scores

7.2NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
6.9QNAP Systems, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
CAPEC-129Pointer Manipulation
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo