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

Medium 4.3 Published 6 Feb 2026 Updated 6 Feb 2026

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

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: None listed

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

Which versions are affected by CVE-2026-25642?

It affects 1 product.

Products include 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.

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-2026-25642 being exploited?

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

Sources

Also known as GHSA-x74j-jmf9-534w.