CVE-2025-66514

Name: CVE-2025-66514
Creator: NVD / NIST
Published: 2025-12-05T18:15:57.457+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.4/10EPSS 0.20%

Last modified Jun 17, 2026

CVE-2025-66514 is a medium-severity vulnerability rated 5.4/10 on the CVSS scale. 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. EPSS estimates a 0.20% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

5.4/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

EPSS Probability

0.20%

10.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Nextcloud	Mail	< 5.5.3

References

https://github.com/nextcloud/mail/commit/c64fcc3b79e0c089b5e1d2e04a07bfa740b2ac09Patch
https://github.com/nextcloud/mail/pull/11740Issue Tracking, Patch
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-v394-8gpc-6fv5Patch, Vendor Advisory
https://hackerone.com/reports/3357036Permissions Required, Vendor Advisory

Timeline

Published: Dec 5, 2025
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2025-66514?

How severe is CVE-2025-66514?

CVE-2025-66514 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 0.20% probability of exploitation in the next 30 days.

How do I fix CVE-2025-66514?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-66514?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST