---
id: CVE-2026-6342
title: >-
  Mattermost Plugins versions <=11.5 11.1.5 10.13.11 11.3.4.0 fail to
  appropriately check for valid namespaces which allows plugin users to create
  subscriptions to groups that were not whitelisted via creating groups that
  share the same pr…
summary: >-
  Mattermost Plugins versions <=11.5 11.1.5 10.13.11 11.3.4.0 fail to
  appropriately check for valid namespaces which allows plugin users to create
  subscriptions to groups that were not whitelisted via creating groups that
  share the same pr…
severity: medium
cvss: 4.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N'
cwe:
  - CWE-863
vendor: mattermost
product: mattermost_server
affected:
  - 'mattermost_server >= 10.13.0, <= 10.13.11'
  - 'mattermost_server >= 11.1.0, <= 11.1.5'
  - 'mattermost_server >= 11.3.0, <= 11.3.4'
published: '2026-05-18'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T20:10:00.190'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-6342'
references:
  - url: 'https://mattermost.com/security-updates'
    label: responsibledisclosure@mattermost.com
tags:
  - nvd
epss: 0.00254
epssPercentile: 0.15791
ingestedAt: '2026-10-14T20:53:12.298Z'
---

## Overview

Mattermost Plugins versions <=11.5 11.1.5 10.13.11 11.3.4.0 fail to appropriately check for valid namespaces which allows plugin users to create subscriptions to groups that were not whitelisted via creating groups that share the same prefix as a whitelisted group. Mattermost Advisory ID: MMSA-2026-00601

## Affected

- `mattermost_server >= 10.13.0, <= 10.13.11`
- `mattermost_server >= 11.1.0, <= 11.1.5`
- `mattermost_server >= 11.3.0, <= 11.3.4`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.