Improper access control in Discourse - CVE-2026-55704
Published: July 29, 2026
Vulnerability identifier: #VU139999
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-2026-55704
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
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 group posts and group mentions endpoints when serializing group activity. A remote user can access those endpoints to disclose shared-draft topic titles and post excerpt/content.
Only users allowed to view a group's activity but not permitted to see shared drafts are able to access the leaked unpublished draft material.
How to mitigate CVE-2026-55704
Install security update from vendor's website.