Vulnerability · Published May 18, 2026 · Assigned by Mattermost

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

Low 3.5

In plain English

A low-severity security flaw in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 6% of all known vulnerabilities).

Severity (CVSS 3.1)3.5Low

Exploit odds (30 days)0.2%top 93.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 (as reported)

Vendor	Product	Versions
Mattermost	Mattermost	0 – through 6.0.10 – through 5.4.13

Weakness: CWE-754 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:L

References

MMSA-2026-00633 vendor-advisory