# CVE-2026-25642: HedgeDoc security headers for uploaded files were not working

> Attackers can host malicious interactive content via SVG files due to weak security headers, enabling XSS attacks in HedgeDoc.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 6 Feb 2026
- **Updated:** 6 Feb 2026
- **Also known as:** GHSA-x74j-jmf9-534w

## What is CVE-2026-25642?

CVE-2026-25642 is a medium-severity cross-site scripting vulnerability in hedgedoc, published on 6 Feb 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

HedgeDoc is an open source, real-time, collaborative, markdown notes application. Prior to 1.10.6, files served below the /uploads/ endpoint did not use a more strict security-policy. This resulted in a too open Content-Security-Policy and furthermore opened the possibility to host malicious interactive web content (such as fake login forms) using SVG files. This vulnerability is fixed in 1.10.6.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-25642?

It affects 1 product.


Products: Hedgedoc Hedgedoc.

## How do I fix CVE-2026-25642?

No fix has been published for CVE-2026-25642 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-25642 being exploited?

There is no known exploitation of CVE-2026-25642 in the wild and no public exploit code.

## Other vulnerabilities in hedgedoc

- [CVE-2021-29475](https://insights.sbomify.com/CVE-2021-29475/): PDF export allows arbitrary file reads (critical 10.0)
- [CVE-2020-26287](https://insights.sbomify.com/CVE-2020-26287/): Stored XSS in mermaid diagrams (high 8.7)
- [CVE-2021-39175](https://insights.sbomify.com/CVE-2021-39175/): XSS vector in slide mode speaker-view (high 8.1)
- [CVE-2021-29503](https://insights.sbomify.com/CVE-2021-29503/): Improper Neutralization of Script-Related HTML Tags in Notes (high 8.1)
- [CVE-2020-26286](https://insights.sbomify.com/CVE-2020-26286/): Arbitary file upload (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-25642 and fix it if it is affected.

What it is: CVE-2026-25642 is a medium-severity cross-site scripting vulnerability in hedgedoc, published on 6 Feb 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-25642 in the wild and no public exploit code.

Affected product: hedgedoc. 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-2026-25642/ (Markdown: https://insights.sbomify.com/CVE-2026-25642/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-25642
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-25642
- OSV: https://osv.dev/vulnerability/CVE-2026-25642

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-25642/
Summaries are generated and may contain mistakes; the official description above is the record.