CVE-2025-66514 Nextcloud Mail stored HTML injection in subject text
An authenticated user can inject HTML into email subjects in Nextcloud Mail, potentially altering the display of message lists.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2025-66514?
CVE-2025-66514 is a low-severity cross-site scripting vulnerability in nextcloud security-advisories, published on 5 Dec 2025. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2025-66514?
It affects 1 product.
Products include Nextcloud Mail.
How do I fix CVE-2025-66514?
No fix has been published for CVE-2025-66514 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2025-66514 being exploited?
There is no known exploitation of CVE-2025-66514 in the wild and no public exploit code.
Other vulnerabilities in nextcloud security-advisories
- CVE-2021-32652 Missing permission check on email metadata retrieval
- CVE-2022-31132 Unauthenticated SSRF in 3rd party module "cerdic/csstidy"
- CVE-2024-52508 Nextcloud Mail auto configurator can be tricked into sending account information to wrong servers
- CVE-2023-23943 Blind SSRF via server URL input in the Nextcloud Mail app
- CVE-2023-45660 Require strict cookies for image proxy requests in Nextcloud Mail
Sources
Also known as GHSA-v394-8gpc-6fv5.