CVE-2026-91156 json
Discourse: Chat MessageBus delivers read-restricted messages to unauthorized users
published 2026-10-14 26 d ago modified 2026-10-21 19 d ago also BIT-discourse-2026-91156 , EUVD-2026-101300 , GHSA-gh4f-qr62-vx8q
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.5%
- EPSS 0.5% chance of exploitation in 30 days, percentile 41%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- bitnami discourse 2026.1.9, 2026.7.3, 2026.8.1, 2026.9.0
- discourse discourse 2026.1.9, 2026.7.3, 2026.8.1, 2026.9.0
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 25 d ago
Exploit prediction
0.48% chance of exploitation in the next 30 days, higher than 41% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
| OSV | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| bitnami | discourse | <2026.1.9 >=2026.7.0, <2026.7.3 >=2026.8.0, <2026.8.1 >=2026.8.99, <2026.9.0 |
2026.1.9 2026.7.3 2026.8.1 2026.9.0 |
Affected products
- discourse discourse
Classification
- Weakness
-
- CWE-862 Missing Authorization
References
-
github.com
/discourse/discourse/commit/046fb7bfd68a5b95e63dda88c3c73877c5cf9d5e
web
-
github.com
/discourse/discourse/commit/87b31bf60a7827f075634254379a1dcbaba409cb
web
-
github.com
/discourse/discourse/commit/ba74bb404ab4439f5b1f0204e848d62099db8ae1
web
-
github.com
/discourse/discourse/commit/cac1f26f275cec3dc1dd51dfdac2b3d1a4ec50f8
web
-
github.com
/discourse/discourse/security/advisories/GHSA-gh4f-qr62-vx8q
web
-
nvd.nist.gov
/vuln/detail/CVE-2026-91156
web
Sources
- CVE List CVE-2026-91156
- NVD CVE-2026-91156
- OSV BIT-discourse-2026-91156
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.