CVE-2026-26973
MEDIUMCVSS Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
Lifecycle Timeline
2Description
Discourse is an open source discussion platform. Versions prior to 2025.12.2, 2026.1.1, and 2026.2.0 have an IDOR (Insecure Direct Object Reference) in `ReviewableNotesController`. When `enable_category_group_moderation` is enabled, a user belonging to a category moderation group can create or delete their own notes on **any** reviewable in the system, including reviewables in categories they do not moderate. The controller used an unscoped `Reviewable.find` and the `ensure_can_see` guard only checked whether the user could access the review queue in general, not whether they could access the specific reviewable. Only instances with `enable_category_group_moderation` enabled are affected. Staff users (admins/moderators) are not impacted as they already have access to all reviewables. The issue is patched in versions 2025.12.2, 2026.1.1, and 2026.2.0 by scoping the reviewable lookup through `Reviewable.viewable_by(current_user)`. As a workaround, disable the `enable_category_group_moderation` site setting. This removes the attack surface as only staff users will have access to the review queue.
Analysis
Insecure Direct Object References in Discourse ReviewableNotesController allow category moderation group members to create or delete notes on any reviewable in the system regardless of moderation scope when category group moderation is enabled. This authorization bypass affects Discourse versions prior to 2025.12.2, 2026.1.1, and 2026.2.0, enabling users to manipulate moderation records outside their assigned categories. …
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Remediation
Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Monitor vendor channels for patch availability.
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