How severe is CVE-2025-66277?

CVE-2025-66277 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2025-66277 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-66277?

CVE-2025-66277 primarily affects Qnap Qts. In total, 37 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2025-66277?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2025-66277 have an EU (EUVD) identifier?

Yes. CVE-2025-66277 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-207017.

When was CVE-2025-66277 published?

CVE-2025-66277 was published on 2026-02-11 and last updated on 2026-06-17.

CVE-2025-66277

CVE-2025-66277 is a critical-severity vulnerability in Qnap Qts with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-59.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v4: 9.2
EPSS exploit prediction: 1% (46th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-207017
Weakness: CWE-59
Affected product: Qnap Qts
Published: 2026-02-11
Last modified: 2026-06-17

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

Frequently asked questions

What is CVE-2025-66277?: 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
How severe is CVE-2025-66277?: CVE-2025-66277 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2025-66277 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-66277?: CVE-2025-66277 primarily affects Qnap Qts. In total, 37 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-66277?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2025-66277 have an EU (EUVD) identifier?: Yes. CVE-2025-66277 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-207017.
When was CVE-2025-66277 published?: CVE-2025-66277 was published on 2026-02-11 and last updated on 2026-06-17.

References

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

Affected products (37)

cpe:2.3:o:qnap:qts:5.2.0.2737:build_20240417:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.0.2744:build_20240424:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.0.2782:build_20240601:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.0.2802:build_20240620:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.0.2823:build_20240711:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.0.2851:build_20240808:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.0.2860:build_20240817:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.1.2930:build_20241025:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.2.2950:build_20241114:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.3.3006:build_20250108:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.4.3070:build_20250312:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.4.3079:build_20250321:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.4.3092:build_20250403:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.5.3145:build_20250526:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.6.3195:build_20250715:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.6.3229:build_20250818:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.7.3256:build_20250913:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.7.3297:build_20251024:*:*:*:*:*:*
cpe:2.3:o:qnap:qts:5.2.8.3332:build_20251128:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.0.2737:build_20240417:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.0.2782:build_20240601:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.0.2789:build_20240607:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.0.2802:build_20240620:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.0.2823:build_20240711:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.0.2851:build_20240808:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.0.2860:build_20240817:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.1.2929:build_20241025:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.1.2940:build_20241105:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.2.2952:build_20241116:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.3.3006:build_20250108:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.4.3070:build_20250312:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.4.3079:build_20250321:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.5.3138:build_20250519:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.6.3195:build_20250715:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.7.3256:build_20250913:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.7.3297:build_20251024:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.2.8.3321:build_20251117:*:*:*:*:*:*

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