---
id: CVE-2026-6334
title: >-
  Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to enforce
  client identity binding during the OAuth authorization code redemption flow
  which allows an authenticated OAuth client to redeem authorization codes
  issued to a di…
summary: >-
  Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to enforce
  client identity binding during the OAuth authorization code redemption flow
  which allows an authenticated OAuth client to redeem authorization codes
  issued to a di…
severity: low
cvss: 3.1
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:N'
cwe:
  - CWE-305
vendor: mattermost
product: mattermost_server
affected:
  - 'mattermost_server >= 10.11.0, < 10.11.14'
  - 'mattermost_server >= 11.5.0, < 11.5.2'
patched:
  - mattermost_server 11.5.2
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-2026-6334'
references:
  - url: 'https://mattermost.com/security-updates'
    label: responsibledisclosure@mattermost.com
tags:
  - nvd
epss: 0.002
epssPercentile: 0.09175
ingestedAt: '2026-10-14T20:53:12.297Z'
---

## Overview

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to enforce client identity binding during the OAuth authorization code redemption flow which allows an authenticated OAuth client to redeem authorization codes issued to a different client via a crafted token exchange request.. Mattermost Advisory ID: MMSA-2026-00570

## Affected

- `mattermost_server >= 10.11.0, < 10.11.14`
- `mattermost_server >= 11.5.0, < 11.5.2`

## Remediation

Upgrade past the affected range:

- `mattermost_server 11.5.2`