CVE-2026-3471: Opening a window with {{javascript:alert()}} as URL causes crash in the Mattermost Desktop App

Description

Mattermost Desktop App versions <=6.1 6.0.1 5.4.13.0 fail to prevent an invalid URL from loading in a pop-up window in the Mattermost Desktop App which allows a malicious server owner to repeated crash the application via calling {{window.open('javascript:alert()');}}. Mattermost Advisory ID: MMSA-2026-00618

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Attack vector

Network

Complexity

Low

Privileges

None

User interaction

Required

Confidentiality

None

Integrity

None

Availability

High

Scope

Unchanged

Exploitation

Is it being used?

Exploit prediction (EPSS)0.2% · higher than 8% of CVEs

Exploited in the wildNo evidence yet

CISA KEVNot listed

Ransomware campaign useNot known

Affected products

Which versions

MA

Mattermost · Mattermost

through 6.0.1; through 5.4.13 · source: vendor

MD

Mattermost Desktop · Mattermost

through 5.4.13.0; 6.0.0 through 6.0.1; 6.1.0 before 6.2.0 · source: NVD