CVE-2026-91156

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.

CVSS 3.1

7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

0.5% chance of exploitation in the next 30 days; higher than 41% of CVEs (scores of 2026-10-25)

CWE

CWE-862

Published

2026-10-14

Modified

2026-10-14

Record from

the NVD, synced 2026-10-19

References

• https://github.com/discourse/discourse/commit/046fb7bfd68a5b95e63dda88c3c73877c5cf9d5e
• https://github.com/discourse/discourse/commit/87b31bf60a7827f075634254379a1dcbaba409cb
• https://github.com/discourse/discourse/commit/ba74bb404ab4439f5b1f0204e848d62099db8ae1
• https://github.com/discourse/discourse/commit/cac1f26f275cec3dc1dd51dfdac2b3d1a4ec50f8
• https://github.com/discourse/discourse/security/advisories/GHSA-gh4f-qr62-vx8q

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