---
id: CVE-2026-8823
aliases:
  - GHSA-xmfh-3ccg-c9fx
title: Mattermost has an Incorrect Authorization issue
summary: Mattermost has an Incorrect Authorization issue
severity: low
cvss: 3.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L'
vendor: mattermost
product: github.com/mattermost/mattermost-server
ecosystem: go
affected:
  - 'github.com/mattermost/mattermost-server >= 11.7.0, < 11.7.1'
  - 'github.com/mattermost/mattermost-server >= 10.11.0, < 10.11.18'
  - >-
    github.com/mattermost/mattermost/server/v8 <
    8.0.0-20260518160100-9bd77d3fc4d2
patched:
  - github.com/mattermost/mattermost-server 11.7.1
  - github.com/mattermost/mattermost-server 10.11.18
  - github.com/mattermost/mattermost/server/v8 8.0.0-20260518160100-9bd77d3fc4d2
published: '2026-06-22'
updated: '2026-09-22'
sourceUpdated: '2026-09-22T14:45:10.458918105Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-xmfh-3ccg-c9fx'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-8823'
  - url: 'https://github.com/mattermost/mattermost/pull/36487'
  - url: >-
      https://github.com/mattermost/mattermost/commit/7972fc53f5c0b0175879a9737308a87b42db1f0b
  - url: >-
      https://github.com/mattermost/mattermost/commit/9bd77d3fc4d2af3f7f0259a205174e76a1a276e1
  - url: >-
      https://github.com/mattermost/mattermost/commit/c9bf3609fb9a3e5c2de94c50742c9b91fd723e3d
  - url: >-
      https://github.com/mattermost/mattermost/commit/d9a55e394cd5bc15edb49e9606bec8fec03ac4c6
  - url: 'https://docs.mattermost.com/security-guide/security-updates'
  - url: 'https://github.com/mattermost/mattermost'
  - url: 'https://github.com/mattermost/mattermost/releases/tag/v10.11.18'
  - url: 'https://github.com/mattermost/mattermost/releases/tag/v11.7.1'
  - url: 'https://github.com/advisories/GHSA-xmfh-3ccg-c9fx'
tags:
  - osv
  - go
  - ghsa
epss: 0.00318
epssPercentile: 0.22038
cwe:
  - CWE-863
ingestedAt: '2026-09-22T15:05:01.074Z'
---

## Overview

Mattermost versions 11.7.x <= 11.7.0, 10.11.x <= 10.11.17 fail to validate bot targets when demoting users to guests which allows a lower-privileged administrator to degrade arbitrary bot accounts via the standard demote-user API.. Mattermost Advisory ID: MMSA-2026-00669

## Affected packages

- `github.com/mattermost/mattermost-server >= 11.7.0, < 11.7.1`
- `github.com/mattermost/mattermost-server >= 10.11.0, < 10.11.18`
- `github.com/mattermost/mattermost/server/v8 < 8.0.0-20260518160100-9bd77d3fc4d2`

## Remediation

Upgrade to a patched release:

- `github.com/mattermost/mattermost-server 11.7.1`
- `github.com/mattermost/mattermost-server 10.11.18`
- `github.com/mattermost/mattermost/server/v8 8.0.0-20260518160100-9bd77d3fc4d2`