How severe is CVE-2025-53591?

CVE-2025-53591 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2025-53591 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-53591?

CVE-2025-53591 primarily affects Qnap Quts Hero. In total, 34 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2025-53591?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2025-53591 have an EU (EUVD) identifier?

Yes. CVE-2025-53591 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-0681.

When was CVE-2025-53591 published?

CVE-2025-53591 was published on 2026-01-02 and last updated on 2026-06-17.

CVE-2025-53591

CVE-2025-53591 is a medium-severity vulnerability in Qnap Quts Hero with a CVSS 3.x base score of 6.5. 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-134.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v4: 1.2
EPSS exploit prediction: 0% (20th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-0681
Weakness: CWE-134
Affected product: Qnap Quts Hero
Published: 2026-01-02
Last modified: 2026-06-17

Description

A use of externally-controlled format string vulnerability has been reported to affect several QNAP operating system versions. If a remote attacker gains an administrator account, they can then exploit the vulnerability to obtain secret data or modify memory. We have already fixed the vulnerability in the following versions: QTS 5.2.7.3256 build 20250913 and later QuTS hero h5.2.7.3256 build 20250913 and later QuTS hero h5.3.1.3250 build 20250912 and later

Frequently asked questions

What is CVE-2025-53591?: A use of externally-controlled format string vulnerability has been reported to affect several QNAP operating system versions. If a remote attacker gains an administrator account, they can then exploit the vulnerability to obtain secret data or modify memory. We have already fixed the vulnerability in the following versions: QTS 5.2.7.3256 build 20250913 and later QuTS hero h5.2.7.3256 build 20250913 and later QuTS hero h5.3.1.3250 build 20250912 and later
How severe is CVE-2025-53591?: CVE-2025-53591 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2025-53591 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-53591?: CVE-2025-53591 primarily affects Qnap Quts Hero. In total, 34 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-53591?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-53591 have an EU (EUVD) identifier?: Yes. CVE-2025-53591 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-0681.
When was CVE-2025-53591 published?: CVE-2025-53591 was published on 2026-01-02 and last updated on 2026-06-17.

References

https://www.qnap.com/en/security-advisory/qsa-25-50

Affected products (34)

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:h5.3.0.3115:build_20250430:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.3.0.3145:build_20250530:*:*:*:*:*:*
cpe:2.3:o:qnap:quts_hero:h5.3.0.3192:build_20250716:*:*:*:*:*:*
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:*:*:*:*:*:*

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