PT-2026-26425 · Discourse · Discourse

Davidtaylorhq · Published 2026-03-19 · Updated 2026-03-27 · CVE-2026-33393

Positive Technologies (AI Summary)

CVSS v3.1

4.3

Medium

Base vector

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

Name of the Vulnerable Software and Affected Versions Discourse versions prior to 2026.3.0-latest.1 Discourse versions prior to 2026.2.1 Discourse versions prior to 2026.1.2

Description Discourse is an open-source discussion platform. The allowed spam host domains check utilized String#end with? without proper domain boundary validation. This allowed domains, such as attacker-example.com, to circumvent spam protection when example.com was allowlisted. The issue stemmed from a lack of requirement for an exact match or a proper subdomain match (preceded by .) to prevent suffix-based bypass of newuser spam host threshold.

Recommendations Update to Discourse version 2026.3.0-latest.1 or later. Update to Discourse version 2026.2.1 or later. Update to Discourse version 2026.1.2 or later.

Exploit

Fix

Improper Access Control

Weakness Enumeration

CWE-284

Related Identifiers

BIT-DISCOURSE-2026-33393

CVE-2026-33393

GHSA-95R5-P6QR-HGW6

Affected Products

Discourse

References · 9

• 🔥 https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33393.json · Exploit
• https://github.com/discourse/discourse/commit/d8467b9fbb3d9ed6047b4e508d3fef88a37b8a02 · Patch
• https://github.com/discourse/discourse/security/advisories/GHSA-95r5-p6qr-hgw6 · Vendor Advisory
• https://github.com/discourse/discourse/commit/80b19c15fe9c7bc890d1a54f454c8446312ac6d2 · Patch
• https://github.com/discourse/discourse/commit/f99099cfbc6b76fe39d6fa2daa48efd69497fb8e · Patch
• https://osv.dev/vulnerability/CVE-2026-33393 · Vendor Advisory
• https://osv.dev/vulnerability/BIT-discourse-2026-33393 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-33393 · Security Note
• https://twitter.com/CVEnew/status/2034891616058495432 · Twitter Post