How severe is CVE-2025-66514?

CVE-2025-66514 has a CVSS 3.x base score of 3.5, rated low severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2025-66514 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-66514?

CVE-2025-66514 affects Nextcloud Mail. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-66514?

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

Does CVE-2025-66514 have an EU (EUVD) identifier?

Yes. CVE-2025-66514 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-201464.

When was CVE-2025-66514 published?

CVE-2025-66514 was published on 2025-12-05 and last updated on 2026-06-17.

CVE-2025-66514

CVE-2025-66514 is a low-severity vulnerability in Nextcloud Mail with a CVSS 3.x base score of 3.5. 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-79.

Key facts

Severity: Low (CVSS 3.x base score 3.5)
EPSS exploit prediction: 0% (11th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-201464
Weakness: CWE-79
Affected product: Nextcloud Mail
Published: 2025-12-05
Last modified: 2026-06-17

Description

Nextcloud Mail is the mail app for Nextcloud, a self-hosted productivity platform. Prior to 5.5.3, a stored HTML injection in the Mail app's message list allowed an authenticated user to inject HTML into the email subjects. Javascript was correctly blocked by the content security policy of the Nextcloud Server code.

Frequently asked questions

What is CVE-2025-66514?: Nextcloud Mail is the mail app for Nextcloud, a self-hosted productivity platform. Prior to 5.5.3, a stored HTML injection in the Mail app's message list allowed an authenticated user to inject HTML into the email subjects. Javascript was correctly blocked by the content security policy of the Nextcloud Server code.
How severe is CVE-2025-66514?: CVE-2025-66514 has a CVSS 3.x base score of 3.5, rated low severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2025-66514 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-66514?: CVE-2025-66514 affects Nextcloud Mail. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-66514?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-66514 have an EU (EUVD) identifier?: Yes. CVE-2025-66514 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-201464.
When was CVE-2025-66514 published?: CVE-2025-66514 was published on 2025-12-05 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:nextcloud:mail:*:*:*:*:*:nextcloud:*:*

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