CVE-2026-72722: Discourse

Medium severity, CVSS 4.3. EPSS: 0.4% chance of exploitation in the next 30 days.

Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, TopicLink.extract_from, TopicLink.ensure_entry_for, and TopicLink.duplicate_lookup do not consistently enforce Guardian.can_see? checks when processing internal links. An authenticated user can submit links to restricted topics, private messages, or hidden posts and receive canonicalized slugs or titles in the composer_messages duplicate_lookup response even though the targets are not visible to that user. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.

Affected products

• Discourse Discourse: before 2026.1.6 (fixed in 2026.1.6); from 2026.5.0-latest, before 2026.5.2 (fixed in 2026.5.2); from 2026.6.0-latest, before 2026.6.1 (fixed in 2026.6.1); from 2026.7.0-latest, before 2026.7.0 (fixed in 2026.7.0)

Published 2026-08-10. Last modified 2026-09-08.