Auth bypass in Discourse
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.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Discourse — versions < 2026.1.9, >= 2026.7.0-latest, < 2026.7.3, >= 2026.8.0-latest, < 2026.8.1
Weakness classification (CWE)
References
- github.com/discourse/discourse/security/advisories/GHSA-gh4f-qr62-vx8q
- github.com/discourse/discourse/commit/046fb7bfd68a5b95e63dda88c3c73877c5cf9d5e
- github.com/discourse/discourse/commit/87b31bf60a7827f075634254379a1dcbaba409cb
- github.com/discourse/discourse/commit/ba74bb404ab4439f5b1f0204e848d62099db8ae1
- github.com/discourse/discourse/commit/cac1f26f275cec3dc1dd51dfdac2b3d1a4ec50f8
Frequently asked questions
- What is CVE-2026-91156?
- CVE-2026-91156 is a high-severity vulnerability in Discourse, classified under Missing Authorization. CVSS score: 7.5/10. Published 2026-10-14.
- How severe is CVE-2026-91156?
- High severity. CVSS v3 base score is 7.5 out of 10.