Discourse
CVE-2026-33355
MEDIUM
Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Lifecycle Timeline
2DescriptionGitHub Advisory
Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the /private-posts endpoint did not apply post-type visibility filtering, allowing regular PM participants to see whisper posts in PM topics they had access to. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. No known workarounds are available.
AnalysisAI
A post-type visibility filtering bypass in Discourse's /private-posts endpoint allows authenticated users with access to private message (PM) topics to view whisper posts that should be restricted to specific recipients. This information disclosure vulnerability affects Discourse versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, and requires only low-privilege user authentication to exploit. …
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Vulnerability AssessmentAI
| Risk Assessment | The CVSS 3.1 vector (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N) yields a score of 6.5, indicating medium severity with high confidentiality impact but no integrity or availability compromise. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker with a regular user account gains access to a private message topic (e.g., by being invited to a project discussion). Once authenticated and with PM topic membership established, the attacker calls the `/private-posts` endpoint via the Discourse API or web interface. … |
| Remediation | Immediately upgrade Discourse to version 2026.1.2, 2026.2.1, or 2026.3.0-latest.1 depending on your release track. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. …
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