CVE-2026-33393CWE-284

Discourse fixes loose hostname matching in spam host allowlist

Medium · published March 19, 2026

CVSS v3.1
4.3
EPSS
0%
Percentile
28.2
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
4.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00356 · 28.2th percentile
Weakness
CWE-284 · Improper Access Control
Published
2026-03-19T22:04Z
EPSS history
Timeline
  • 19 MAR 22:04Z
    Discourse fixes loose hostname matching in spam host allowlist
    cvelistv5