---
id: CVE-2026-3433
aliases:
  - GHSA-rp4v-qc77-phm4
title: >-
  Mattermost doesn't restrict role_updated websocket event broadcasts to members
  of the affected team or channel
summary: >-
  Mattermost doesn't restrict role_updated websocket event broadcasts to members
  of the affected team or channel
severity: medium
cvss: 4.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N'
vendor: mattermost
product: github.com/mattermost/mattermost-server
ecosystem: go
affected:
  - 'github.com/mattermost/mattermost-server >= 11.6.0, < 11.6.1'
  - 'github.com/mattermost/mattermost-server >= 11.5.0, < 11.5.5'
  - 'github.com/mattermost/mattermost-server >= 10.11.0, < 10.11.17'
  - >-
    github.com/mattermost/mattermost/server/v8 >=
    8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260504071740-9408b98025d7
patched:
  - github.com/mattermost/mattermost-server 11.6.1
  - github.com/mattermost/mattermost-server 11.5.5
  - github.com/mattermost/mattermost-server 10.11.17
  - github.com/mattermost/mattermost/server/v8 8.0.0-20260504071740-9408b98025d7
published: '2026-06-12'
updated: '2026-08-24'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-rp4v-qc77-phm4'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-3433'
  - url: 'https://github.com/mattermost/mattermost/pull/35497'
  - url: 'https://github.com/mattermost/mattermost/pull/36256'
  - url: 'https://github.com/mattermost/mattermost/pull/36257'
  - url: 'https://github.com/mattermost/mattermost/pull/36341'
  - url: >-
      https://github.com/mattermost/mattermost/commit/0a0ab0d54d899d308bd1352cc577036917500318
  - url: >-
      https://github.com/mattermost/mattermost/commit/7425c6817bf244f976c729f8a73cecac8039a1e1
  - url: >-
      https://github.com/mattermost/mattermost/commit/9408b98025d7364d7dfe7cdb28fcd109b1b595a6
  - url: >-
      https://github.com/mattermost/mattermost/commit/a30a331a29b9766d46716d4252056d7b74e66da0
  - url: 'https://github.com/mattermost/mattermost'
  - url: 'https://github.com/mattermost/mattermost/releases/tag/v10.11.16'
  - url: 'https://github.com/mattermost/mattermost/releases/tag/v11.5.5'
  - url: 'https://github.com/mattermost/mattermost/releases/tag/v11.6.2'
  - url: 'https://github.com/mattermost/mattermost/releases/tag/v11.7.0'
  - url: 'https://mattermost.com/security-updates'
tags:
  - osv
  - go
epss: 0.00301
epssPercentile: 0.20293
ingestedAt: '2026-08-25T19:26:23.194Z'
---

## Overview

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to restrict role_updated websocket event broadcasts to members of the affected team or channel, which allows an authenticated attacker with guest-level access to observe permission scheme change notifications for private teams they are not a member of via the websocket connection. Mattermost Advisory ID: MMSA-2026-00616

## Affected packages

- `github.com/mattermost/mattermost-server >= 11.6.0, < 11.6.1`
- `github.com/mattermost/mattermost-server >= 11.5.0, < 11.5.5`
- `github.com/mattermost/mattermost-server >= 10.11.0, < 10.11.17`
- `github.com/mattermost/mattermost/server/v8 >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260504071740-9408b98025d7`

## Remediation

Upgrade to a patched release:

- `github.com/mattermost/mattermost-server 11.6.1`
- `github.com/mattermost/mattermost-server 11.5.5`
- `github.com/mattermost/mattermost-server 10.11.17`
- `github.com/mattermost/mattermost/server/v8 8.0.0-20260504071740-9408b98025d7`