CVE-2026-47264: Discourse

Medium severity, CVSS 5.3. EPSS: 0.4% chance of exploitation in the next 30 days.

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.4, 2026.3.0-latest to before 2026.3.1, and 2026.4.0-latest to before 2026.4.1, DetailedTagSerializer#tag_group_names returned every tag group a tag belonged to without filtering against the requesting user's visibility. With SiteSetting.tags_listed_by_group enabled, anonymous and unprivileged users hitting TagsController#info (which is exempt from requires_login) could read the names of tag groups restricted to specific user groups or non-visible categories. This issue has been patched in versions 2026.1.4, 2026.3.1, 2026.4.1, and 2026.5.0-latest.1.

Affected products

• Discourse Discourse: before 2026.1.0 (fixed in 2026.1.0); from 2026.1.0, before 2026.1.4 (fixed in 2026.1.4); from 2026.3.0, before 2026.3.1 (fixed in 2026.3.1); from 2026.4.0, before 2026.4.1 (fixed in 2026.4.1); version 2026.5.0 only

Published 2026-06-12. Last modified 2026-06-17.