CVE-2025-66514
Low
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.
SeverityLow
CVSS3.5
Exploit probability—
Product
Nextcloud Mail
PublishedDec 5, 2025
First seenDec 5, 2025
Weakness typeCWE-79Cross-site scripting (XSS)
How to fix
Update
- nextcloud mail5.5.3 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| nextcloud mail | v < 5.5.3 | 5.5.3 |
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