MessageBus Vulnerability in Discourse Discussion Platform
CVE-2026-91156

7.5HIGH

Key Information:

Vendor

Discourse
Status
Discourse
Vendor
CVE Published:
14 October 2026

What is CVE-2026-91156?

A vulnerability in the MessageBus component of the Discourse open-source discussion platform could allow authenticated users to receive messages from chat channels that should be view-restricted based on the site's group settings. Although users were not permitted to modify or create messages, the flaw exposed live messages and recent content from the MessageBus backlog. This security gap necessitated immediate attention and has been resolved in subsequent versions.

Affected Version(s)

discourse < 2026.1.9 < 2026.1.9

discourse >= 2026.7.0-latest, < 2026.7.3 < 2026.7.0-latest, 2026.7.3

discourse >= 2026.8.0-latest, < 2026.8.1 < 2026.8.0-latest, 2026.8.1

References

https://github.com/discourse/discourse/security/advisorie...
x_refsource_CONFIRM
https://github.com/discourse/discourse/commit/046fb7bfd68...
x_refsource_MISC
https://github.com/discourse/discourse/commit/87b31bf60a7...
x_refsource_MISC

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
High
Integrity:
None
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.