---
id: CVE-2026-91156
title: Discourse is an open-source discussion platform
summary: >-
  Discourse is an open-source discussion platform. Prior to 2026.9.0, 2026.8.1,
  2026.7.3, and 2026.1.9, MessageBus audience calculation could deliver messages
  from a read-restricted category chat channel to an authenticated user who
  could …
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-862
published: '2026-10-14'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T18:19:33.973'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-91156'
references:
  - url: >-
      https://github.com/discourse/discourse/commit/046fb7bfd68a5b95e63dda88c3c73877c5cf9d5e
    label: security-advisories@github.com
  - url: >-
      https://github.com/discourse/discourse/commit/87b31bf60a7827f075634254379a1dcbaba409cb
    label: security-advisories@github.com
  - url: >-
      https://github.com/discourse/discourse/commit/ba74bb404ab4439f5b1f0204e848d62099db8ae1
    label: security-advisories@github.com
  - url: >-
      https://github.com/discourse/discourse/commit/cac1f26f275cec3dc1dd51dfdac2b3d1a4ec50f8
    label: security-advisories@github.com
  - url: >-
      https://github.com/discourse/discourse/security/advisories/GHSA-gh4f-qr62-vx8q
    label: security-advisories@github.com
tags:
  - nvd
ingestedAt: '2026-10-14T16:40:32.133Z'
---

## Overview

Discourse is an open-source discussion platform. Prior to 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9, MessageBus audience calculation could deliver messages from a read-restricted category chat channel to an authenticated user who could view the category but was not allowed to use Chat under the site's group restrictions. The publication path bounded events by category visibility without also enforcing Chat eligibility, exposing live and recent message content available in the MessageBus backlog. The issue does not permit retrieval of the channel's full history through the Chat API and does not permit message creation or modification. This issue is fixed in versions 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9.

## Remediation

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