Improper access control in Discourse - CVE-2026-33300
Published: July 1, 2026
Vulnerability identifier: #VU136144
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-33300
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Civilized Discourse Construction Kit, Inc.
Affected software:
Discourse
Discourse
Detailed vulnerability description
The vulnerability allows a remote user to disclose sensitive information.
The vulnerability exists due to improper access control in the Category Chatables Controller show action when handling requests to the `category-chatables` endpoint. A remote user can send a request to obtain hidden group names and user count information to disclose sensitive information.
The issue exposes hidden group metadata to moderators.
How to mitigate CVE-2026-33300
Install security update from vendor's website.