CVE-2026-4274

Published: Mar 26, 2026Modified: Mar 26, 2026

5.4

Vector

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

Exploitability: 2.8 / Impact: 2.5

Source: responsibledisclosure@mattermost.com (Secondary)

Description

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to restrict team-level access when processing membership sync from a remote cluster, which allows a malicious remote cluster to grant a user access to an entire private team instead of only the shared channel via sending crafted membership sync messages that trigger team membership assignment. Mattermost Advisory ID: MMSA-2026-00574

Affected (4)

Products: Mattermost: Mattermost Server

Mattermost

1 product

Mattermost Server

Configuration A

4 vulnerable

Vulnerable Software	Affected Versions
Mattermost Mattermost Server	From 10.11.0 to 10.11.11
Mattermost Mattermost Server	From 11.2.0 to 11.2.3
Mattermost Mattermost Server	From 11.3.0 to 11.3.2
Mattermost Mattermost Server	From 11.4.0 to 11.4.1

Related CWEs

CWE-863

Incorrect Authorization

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.

References (1)

https://mattermost.com/security-updates

Source: responsibledisclosure@mattermost.com

Vendor Advisory

Timeline

No history available yet.