🛡️ CVE-2026-33393 — discourse

🟡 CVSS 5.0 — Medium ✅ No Known Exploit CWE-284 OSV
5.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Discourse fixes loose hostname matching in spam host allowlist

Discourse is an open-source discussion platform. Prior to versions 2026.3.0, 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, 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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity low, availability none.

Weakness class

CVE-2026-33393 is classified as CWE-284: Improper Access Control. The software does not restrict an action to the actors that should be allowed to perform it.

Affected software

CVE-2026-33393 is recorded against 1 package.

  • discourse

Timeline and source

Published on 27 March 2026 and last revised on 17 June 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from OSV.

References

github.com (Web)
github.com (Web)
github.com (Web)
github.com (Web)
nvd.nist.gov (Web)

Details

Severity MEDIUM
CVSS Score 5.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
CWE CWE-284
Public Exploit ✅ No
Source OSV
Published 2026-03-27
Updated 2026-08-12
Modified 2026-06-17

Affected Packages

Software From version Fixed in
discourse — —

Similar Threats

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