CVE-2026-4643: Calling window.close() from server-side content causes crash in the Mattermost Desktop App

Severity: low (CVSS 3.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-18 · updated 2026-06-17
Weakness: CWE-754

Description

Mattermost Desktop App versions <=6.1 6.0.1 5.4.13.0 fail to prevent server-rendered content from closing an underlying application view in the Mattermost Desktop App which allows a malicious server or plugin to crash the desktop client via invoking {{window.close()}} in the renderer context, leading to a denial of service condition at the client level. Mattermost Advisory ID: MMSA-2026-00633

Affected products

Mattermost Desktop: through 5.4.13.0; from 6.0.0 through 6.0.1; from 6.1.0 before 6.2.0 — fixed in 6.2.0

How to fix

Upgrade to a fixed version: Mattermost Desktop 6.2.0. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

Get alerted when CVE-2026-4643 or the next vulnerability affects your stack