Discourse up to 2025.12.1/2026.1.0 enable_category_group_moderation authorization

Summaryinfo

A vulnerability classified as problematic was found in Discourse up to 2025.12.1/2026.1.0. Affected by this vulnerability is the function enable_category_group_moderation. Executing a manipulation can lead to authorization. This vulnerability is registered as CVE-2026-26973. It is possible to launch the attack remotely. No exploit is available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as problematic was found in Discourse up to 2025.12.1/2026.1.0. This vulnerability affects the function enable_category_group_moderation. The manipulation with an unknown input leads to a authorization vulnerability. The CWE definition for the vulnerability is CWE-863. The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions. As an impact it is known to affect integrity. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-26973 since 02/16/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available.

Upgrading to version 2025.12.2, 2026.1.1 or 2026.2.0 eliminates this vulnerability.

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Type

• Chat Software

Name

• Discourse

Version

• 2025.12.0
• 2025.12.1
• 2026.0
• 2026.1.0

License

• open-source

Website

• Product: https://github.com/discourse/discourse/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Discussion