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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-91156
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-14 16:17:56 UTC
Updated2026-10-14 18:19:33 UTC
DescriptionDiscourse 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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Problem Types: CWE-862 | CWE-862 CWE-862: Missing Authorization

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Discourse Discourse affected < 2026.1.9 Not specified
CNA Discourse Discourse affected >= 2026.7.0-latest, < 2026.7.3 Not specified
CNA Discourse Discourse affected >= 2026.8.0-latest, < 2026.8.1 Not specified
CNA Discourse Discourse affected >= 2026.9.0-latest, < 2026.9.0 Not specified

References

ReferenceSourceLinkTags
github.com/discourse/discourse/commit/87b31bf60a7827f075634254379a1dcbab... [email protected] github.com
github.com/discourse/discourse/commit/cac1f26f275cec3dc1dd51dfdac2b3d1a4... [email protected] github.com
github.com/discourse/discourse/security/advisories/GHSA-gh4f-qr62-vx8q [email protected] github.com
github.com/discourse/discourse/commit/046fb7bfd68a5b95e63dda88c3c73877c5... [email protected] github.com
github.com/discourse/discourse/commit/ba74bb404ab4439f5b1f0204e848d62099... [email protected] github.com
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