CVE-2026-1628 Mattermost allows external websites to open within the app, exposing preload functionality to non-trusted sites.

Q: Is CVE-2026-1628 being exploited?

There is no known exploitation of CVE-2026-1628 in the wild and no public exploit code.

Q: How do I fix CVE-2026-1628?

No fix has been published for CVE-2026-1628 yet. Limit exposure of the affected software until one is available.

Medium 4.6 Published 2 Mar 2026 Updated 2 Mar 2026

Mattermost Desktop App allows malicious servers to expose preload script functionality to untrusted sites, potentially enabling code execution.

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-2026-1628?

CVE-2026-1628 is a medium-severity code injection vulnerability in Mattermost, published on 2 Mar 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

Mattermost Desktop App versions <=5.13.3 fail to attach listeners restricting navigation to external sites within the Mattermost app which allows a malicious server to expose preload script functionality to untrusted servers via having a user open an external link in their Mattermost server. Mattermost Advisory ID: MMSA-2026-00596

Weakness: CWE-829

Which versions are affected by CVE-2026-1628?

It affects 1 product.

Products include Mattermost Mattermost Desktop.

How do I fix CVE-2026-1628?

No fix has been published for CVE-2026-1628 yet. Limit exposure of the affected software until one is available.

Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.

Is CVE-2026-1628 being exploited?

There is no known exploitation of CVE-2026-1628 in the wild and no public exploit code.

Sources

Also known as GHSA-4q28-37qp-xh4g.