CVE-2025-55035 Mattermost Desktop DoS when user has basic authentication server configured
An attacker can deny service to Mattermost Desktop users by forcing an unclosable modal popup when a malicious server with basic authentication is configured.
- 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-2025-55035?
CVE-2025-55035 is a medium-severity denial of service vulnerability in Mattermost, published on 16 Oct 2025. 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
Mattermost Desktop App versions <=5.13.0 fail to manage modals in the Mattermost Desktop App that stops a user with a server that uses basic authentication from accessing their server which allows an attacker that provides a malicious server to the user to deny use of the Desktop App via having the user configure the malicious server and forcing a modal popup that cannot be closed.
Weakness: CWE-754
Which versions are affected by CVE-2025-55035?
It affects 1 product.
Products include Mattermost Mattermost Desktop.
How do I fix CVE-2025-55035?
No fix has been published for CVE-2025-55035 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-55035 being exploited?
There is no known exploitation of CVE-2025-55035 in the wild and no public exploit code.
Other vulnerabilities in Mattermost
Sources
Also known as GHSA-3359-25fv-h37v.