CVE-2026-75588 Mattermost Desktop App plugin popout scheme validation bypass
An attacker can bypass URL scheme validation to load plugin popout windows over insecure connections in the Mattermost Desktop App.
- 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-2026-75588?
CVE-2026-75588 is a low-severity vulnerability in Mattermost, published on 17 Sep 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 <=6.2 6.2.2.0 fail to validate the URL scheme when checking whether a target URL is internal to the connected server, which allows a network-positioned attacker to load a plugin popout window over an insecure connection via a link using a downgraded URL scheme. Mattermost Advisory ID: MMSA-2026-00717
Weakness: CWE-1287
Which versions are affected by CVE-2026-75588?
It affects 1 product.
Products include Mattermost Mattermost Desktop.
How do I fix CVE-2026-75588?
No fix has been published for CVE-2026-75588 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-75588 being exploited?
There is no known exploitation of CVE-2026-75588 in the wild and no public exploit code.
Other vulnerabilities in Mattermost
Sources
Also known as GHSA-p8rx-2r7q-5wfv.