---
id: CVE-2026-91181
title: >-
  Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7,
  10.11.x <= 10.11.22 Fail to sanitize Team objects returned by the data
  retention teams endpoint which allows an authenticated user holding only the
  read-only Data …
summary: >-
  Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7,
  10.11.x <= 10.11.22 Fail to sanitize Team objects returned by the data
  retention teams endpoint which allows an authenticated user holding only the
  read-only Data …
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-863
vendor: Mattermost
product: Mattermost
affected:
  - Mattermost >= 11.9.0 <= 11.9.0
  - Mattermost >= 11.8.0 <= 11.8.4
  - Mattermost >= 11.7.0 <= 11.7.7
  - Mattermost >= 10.11.0 <= 10.11.22
published: '2026-09-14'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T19:30:49.967'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-91181'
references:
  - url: 'https://mattermost.com/security-updates'
    label: responsibledisclosure@mattermost.com
tags:
  - nvd
  - cve.org
epss: 0.00387
epssPercentile: 0.30044
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-15T19:15:24.266955Z'
ingestedAt: '2026-09-14T22:16:09.898Z'
---

## Overview

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 Fail to sanitize Team objects returned by the data retention teams endpoint which allows an authenticated user holding only the read-only Data Retention Policy permission to obtain a private team's secret invite_id and email, and use it to join the team without authorization, via GET /api/v4/data_retention/policies/{policy_id}/teams.. Mattermost Advisory ID: MMSA-2026-00702

## Remediation

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