Information disclosure in Discourse - CVE-2026-33355
Published: July 1, 2026
Vulnerability identifier: #VU136128
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-33355
CWE-ID: CWE-200
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 /private-posts endpoint when handling requests for private message topics. A remote user can request the private-posts feed for a PM topic they can access to disclose sensitive information.
Only regular PM participants could view whisper posts in PM topics they already had access to.
How to mitigate CVE-2026-33355
Install security update from vendor's website.