CVE-2026-91132 json
Discourse: Wildcard iframe origin allowlist bypass via authority separators
published 2026-09-24 45 d ago modified 2026-10-01 39 d ago also BIT-discourse-2026-91132 , EUVD-2026-86303 , GHSA-4q3q-hph3-3rvp
- cvss
- 4.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.1%
- EPSS 0.1% chance of exploitation in 30 days, percentile 3%
- public exploits
- 0
- none known
Summary
Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, sites using wildcard patterns in the allowed_iframes setting could accept a crafted iframe URL whose allowlisted suffix appeared after a URL authority separator. The wildcard origin check matched the allowed domain text, while browser URL parsing selected a different attacker-controlled origin. A user with posting privileges could exploit the flaw through a post or a Onebox oEmbed response and cause an attacker-controlled iframe to be rendered independently of the allowlisted domain. Successful exploitation requires a site-configured wildcard iframe pattern and the ability to create a post or trigger an oEmbed request for an attacker-controlled URL. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
Patch / fix
- bitnami discourse 2026.8.0
- discourse discourse 2026.1.8, 2026.6.3, 2026.7.2, 2026.8.0
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 41 d ago
Exploit prediction
0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 4.3 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N |
| OSV | 3.1 | 4.3 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| bitnami | discourse | <2026.8.0 |
2026.8.0 |
Affected products
- discourse discourse
Classification
- Weakness
-
- CWE-346 Origin Validation Error
References
-
github.com
/discourse/discourse/pull/42882
web
-
github.com
/discourse/discourse/commit/80968704c1acb1d2ea2c6011dbf6c02ff13238e5
web
-
github.com
/discourse/discourse/commit/d5ae0940707f95da5bc4562f7b544243e3103f8a
web
-
github.com
/discourse/discourse/commit/d88e02ceb2eede4d8b851d9fe8aef753f3aa40b9
web
-
github.com
/discourse/discourse/commit/db8064f2a2a2a3feb3308a1c932ac61d950c9e56
web
-
github.com
/discourse/discourse/security/advisories/GHSA-4q3q-hph3-3rvp
web
-
nvd.nist.gov
/vuln/detail/CVE-2026-91132
web
Sources
- CVE List CVE-2026-91132
- NVD CVE-2026-91132
- OSV BIT-discourse-2026-91132
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.