CVE-2026-33393
Medium
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.
SeverityMedium
CVSS4.3
Exploit probability—
Product
Discourse
PublishedMar 19, 2026
First seenMar 19, 2026
Weakness typeCWE-284Improper access control
How to fix
Update
- discourse discourse2026.1.2, 2026.2.1 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| discourse discourse | 2026.1.0 ≤ v < 2026.1.2, 2026.2.0 ≤ v < 2026.2.1, 2026.3.0 | 2026.1.2, 2026.2.1 |
Check your version
Choose the product and enter the version you run to see whether it falls in the affected range.
In the Intelligence 360 plan
Attack Surface Management
See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.