CVE-2026-33393
Discourse fixes loose hostname matching in spam host allowlist
CVSS Score
4.3
EPSS Score
0.0%
EPSS Percentile
7th
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.
| CWE | CWE-284 |
| Vendor | discourse |
| Product | discourse |
| Published | Mar 19, 2026 |
| Last Updated | Mar 20, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None
Affected Versions
discourse / discourse
>= 2026.1.0-latest, < 2026.1.2 >= 2026.2.0-latest, < 2026.2.1 = 2026.3.0-latest
References
github.com: https://github.com/discourse/discourse/security/advisories/GHSA-95r5-p6qr-hgw6 github.com: https://github.com/discourse/discourse/commit/80b19c15fe9c7bc890d1a54f454c8446312ac6d2 github.com: https://github.com/discourse/discourse/commit/d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02 github.com: https://github.com/discourse/discourse/commit/f99099cfbc6b76fe39d6fa2daa48efd69497fb8e