CVE-2026-33393
Discourse fixes loose hostname matching in spam host allowlist
- State
- Published
- Severity
- 4.3 Medium
- Published
- Mar 19, 2026
- Updated
- Mar 20, 2026
- Reserved
- Mar 19, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 4.3 Medium | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N | GitHub_M |
Weaknesses
- CWE-284 Improper Access Control
Affected Products
| Product | Versions |
|---|---|
discoursediscourse |
|
References
- https://github.com/discourse/discourse/security/advisories/GHSA-95r5-p6qr-hgw6
- https://github.com/discourse/discourse/commit/80b19c15fe9c7bc890d1a54f454c8446312ac6d2
- https://github.com/discourse/discourse/commit/d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02
- https://github.com/discourse/discourse/commit/f99099cfbc6b76fe39d6fa2daa48efd69497fb8e
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