CVE-2026-40596 MantisBT is vulnerable to XSS and potential account takeover via user font family preference update
Authenticated users can inject HTML via font settings, leading to reflected XSS and potential account takeover in MantisBT.
- 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
What is CVE-2026-40596?
CVE-2026-40596 is a high-severity cross-site scripting vulnerability in mantisbt, published on 22 May 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Mantis Bug Tracker (MantisBT) is an open source issue tracker. Versions 2.11.0 through 2.28.1 allow any authenticated user to inject arbitrary HTML by updating their account's font family. Upon exploitation, an XSS payload would be reflected on every MantisBT page. Leveraging another vulnerability (CSP bypass, see GHSA-9c3j-xm6v-j7j3), the attacker could achieve account takeover. This issue has been fixed in version 2.28.2.
Weakness: CWE-79
Which versions are affected by CVE-2026-40596?
2 open source packages ship an affected version, including mantisbt/mantisbt.
| Package | Affected | Fixed in |
|---|---|---|
mantisbt/mantisbt Packagist | From 2.11.0 | 2.28.2 |
mantisbt/mantisbt Packagist | From 2.11.0 | 2.28.2 |
How do I fix CVE-2026-40596?
Upgrade mantisbt/mantisbt to 2.28.2 or later.
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-2026-40596 being exploited?
There is no known exploitation of CVE-2026-40596 in the wild and no public exploit code.
Sources
Also known as GHSA-j3v9-553h-x28j.