CVE-2026-21865: Discourse

Medium severity, CVSS 6.5. EPSS: 0.3% chance of exploitation in the next 30 days.

Discourse is an open source discussion platform. In versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0, moderators can convert some personal messages to public topics when they shouldn't have access. This issue is patched in versions 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0. As a workaround, site admin can temporarily revoke the moderation role from untrusted moderators or remove the moderator group from the "personal message enabled groups" site setting until the Discourse instance has been upgraded to a version that has been patched.

Affected products

• Discourse Discourse: before 3.5.4 (fixed in 3.5.4); from 2025.11.0, before 2025.11.2 (fixed in 2025.11.2); version 2025.12.0 only; version 2026.1.0 only

Published 2026-01-28. Last modified 2026-06-17.