# 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.

- **Severity:** Low 3.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N`)
- **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 available:** No
- **Published:** 5 Dec 2025
- **Updated:** 8 Dec 2025
- **Also known as:** GHSA-v394-8gpc-6fv5

## 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 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2025-66514?

It affects 1 product.


Products: 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.

## 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](https://insights.sbomify.com/CVE-2021-32652/): Missing permission check on email metadata retrieval (high 8.8)
- [CVE-2022-31132](https://insights.sbomify.com/CVE-2022-31132/): Unauthenticated SSRF in 3rd party module "cerdic/csstidy" (high 8.3)
- [CVE-2024-52508](https://insights.sbomify.com/CVE-2024-52508/): Nextcloud Mail auto configurator can be tricked into sending account information to wrong servers (high 8.2)
- [CVE-2023-23943](https://insights.sbomify.com/CVE-2023-23943/): Blind SSRF via server URL input in the Nextcloud Mail app (medium 5.0)
- [CVE-2023-45660](https://insights.sbomify.com/CVE-2023-45660/): Require strict cookies for image proxy requests in Nextcloud Mail (medium 4.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-66514 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2025-66514 in the wild and no public exploit code.

Affected product: nextcloud security-advisories. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-66514/ (Markdown: https://insights.sbomify.com/CVE-2025-66514/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-66514
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-66514
- OSV: https://osv.dev/vulnerability/CVE-2025-66514

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-66514/
Summaries are generated and may contain mistakes; the official description above is the record.