EUVD-2026-17555Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:L/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:L/I:N/A:N
Lifecycle Timeline
4DescriptionGitHub Advisory
Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, there is possible channel membership inference from chat user search without authorization. This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.
AnalysisAI
Discourse chat user search functionality discloses channel membership information to authenticated users without proper authorization checks, allowing users to infer private channel membership across versions 2026.1.0-2026.1.2, 2026.2.0-2026.2.1, and 2026.3.0-rc1, affecting community administrators and organizations relying on channel privacy. The vulnerability requires authenticated access but carries low confidentiality impact (CVSS 4.3); patches are available in versions 2026.1.3, 2026.2.2, and 2026.3.0.
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Vulnerability AssessmentAI
| Risk Assessment | The CVSS vector (AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N) indicates low impact: network-accessible, low attack complexity, requiring authenticated login, no user interaction, confined scope, and minimal confidentiality loss. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An authenticated user on a Discourse instance performs a chat user search with crafted queries targeting known usernames or profiles, observing subtle differences in search result metadata or presence indicators that correlate with membership in private channels they should not be able to access. By systematically querying users and cross-referencing visible activity patterns, the attacker maps membership in confidential channels (e.g., staff-only discussions, customer-specific groups) without direct access to those channels. … |
| Remediation | Upgrade to patched versions: Discourse 2026.1.3 for the 2026.1.x branch, Discourse 2026.2.2 for the 2026.2.x branch, or Discourse 2026.3.0 or later for the 2026.3.x branch. … Detailed patch versions, workarounds, and compensating controls in full report. |
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