CVE-2025-66514

3.5 LOW 0.3% exploit odds Fix listed XSS Server

What it is

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.

At a glance

Exploitability: Can be exploited over the network with a low-privilege account, but needs a user to act. Limited direct impact.
Exploit odds: 0.3% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2025-12-05 18:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-10-15 21:10 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.3% in the next 30 days (EPSS).
Severity: 3.5 LOW (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2025-12-05 18:15 UTC
Last modified: 2026-10-15 21:10 UTC
Exploit probability: 0.3% · EPSS, next 30 days
Weakness: CWE-79 · Cross-site scripting
Record status: Analyzed

Affected

Nextcloud Mail < 5.5.3

Attack profile CVSS 3.1 · 3.5

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: Required
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: None

Raw vector

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

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2025-66514.md and follow it. Check whether this project is affected by CVE-2025-66514. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record