CVE-2026-33393 json
Discourse fixes loose hostname matching in spam host allowlist
published 2026-03-19 7 mo ago modified 2026-09-08 2 mo ago also BIT-discourse-2026-33393 , EUVD-2026-13338 , GHSA-95r5-p6qr-hgw6
- cvss
- 4.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 18%
- public exploits
- 0
- none known
Summary
Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the `allowed_spam_host_domains` check used `String#end_with?` without domain boundary validation, allowing domains like `attacker-example.com` to bypass spam protection when `example.com` was allowlisted. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 require exact match or proper subdomain match (preceded by `.`) to prevent suffix-based bypass of `newuser_spam_host_threshold`. No known workarounds are available.
Patch / fix
- bitnami discourse 2026.1.2, 2026.2.1, 2026.3.0
- discourse discourse 2026.1.2, 2026.2.1
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 7 mo ago
Exploit prediction
0.27% chance of exploitation in the next 30 days, higher than 18% 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 | >=2026.1.0, <2026.1.2 >=2026.2.0, <2026.2.1 >=2026.3.0, <2026.3.0 |
2026.1.2 2026.2.1 2026.3.0 |
Affected products
- discourse discourse
Classification
- Weakness
-
- CWE-284 Improper Access Control
References
-
github.com
/discourse/discourse/commit/80b19c15fe9c7bc890d1a54f454c8446312ac6d2
patch
-
github.com
/discourse/discourse/commit/d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02
patch
-
github.com
/discourse/discourse/commit/f99099cfbc6b76fe39d6fa2daa48efd69497fb8e
patch
-
github.com
/discourse/discourse/security/advisories/GHSA-95r5-p6qr-hgw6
vendor-advisory, advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-33393
web
Sources
- CVE List CVE-2026-33393
- NVD CVE-2026-33393
- OSV BIT-discourse-2026-33393
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.