All vulnerabilities
CVE-2026-91156GHSA-gh4f-qr62-vx8q

Discourse: Chat MessageBus delivers read-restricted messages to unauthorized users

discourse discourseApplications & CMS
Open in ThreatlineRecord JSON
CVSS
7.5High
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.48%Chance of exploitation activity in the next 30 days, higher than 40% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in2026.9.0Also 2026.8.1, 2026.7.3 and 1 moreGitHub
Published14 Oct 2026Updated 14 Oct 2026CVE List

What fixes it

  • 2026.9.0Discourse, otherGitHub
  • 2026.8.1Discourse, otherGitHub
  • 2026.7.3Discourse, otherGitHub
  • 2026.1.9Discourse, otherGitHub

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

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.

Text from CVE List

Affected versions 8

  • discourseaffected: < 2026.1.9CVE List
  • discourseaffected: >= 2026.7.0-latest, < 2026.7.3CVE List
  • discourseaffected: >= 2026.8.0-latest, < 2026.8.1CVE List
  • discourseaffected: >= 2026.9.0-latest, < 2026.9.0CVE List
  • Discourse, other>= 0GitHub
  • Discourse, other>= 2026.8.0-latestGitHub
  • Discourse, other>= 2026.7.0-latestGitHub
  • Discourse, other>= 2026.1.0-latestGitHub

References 5