Vulnerability Report

CVE-2026-33393

Title: Spam Host Domain Bypass in Discourse

Other

Proof Of Concept

No public PoC currently indexed for CVE-2026-33393.

CWE Category CWE-284

Published Date Mar 19, 2026

Modified Date Mar 24, 2026

Exploit Status Not Found

Score 4.3 CVSS v3.1

Exploit Probability (EPSS)

0.05%

Vulnerability Summary

CVE-2026-33393: 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.

Impacted Vendors

discourse 1

Reference Links

https://github.com/discourse/discourse/commit/80b19c15fe9c7bc890d1a54f454c8446312ac6d2 https://github.com/discourse/discourse/commit/d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02 https://github.com/discourse/discourse/commit/f99099cfbc6b76fe39d6fa2daa48efd69497fb8e https://github.com/discourse/discourse/security/advisories/GHSA-95r5-p6qr-hgw6

CVSS v3.1

Source Entity [email protected]

Severity MEDIUM

4.3

Attack Vector

NETWORK

Complexity

LOW

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

UNCHANGED

RAW VECTOR CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

Associated Attack Patterns (CAPEC)

Total: Patterns

CVE-2026-33393 Exploits & PoCs (Proof Of Concept)

No public PoCs found in our database for this CVE.

March 24, 2026 MODIFIED

Vulnerability data updated via NVD.

March 24, 2026 MODIFIED

Vulnerability data updated via NVD.

March 20, 2026 MODIFIED

Vulnerability data updated via NVD.

March 19, 2026 MODIFIED

Vulnerability data updated via NVD.

Attack Vector Matrix

Access Vector NETWORK

Complexity LOW

Privileges N/A

Interaction NONE

CVSS Vector String


                                    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

Affected Stack

No specific products linked.