{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-31869","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","state":"PUBLISHED","assignerShortName":"GitHub_M","dateReserved":"2026-03-09T19:02:25.014Z","datePublished":"2026-03-20T03:10:43.213Z","dateUpdated":"2026-03-20T17:18:59.947Z"},"containers":{"cna":{"title":"Discourse: Composer mentions endpoint leaks hidden group membership through PM `allowed_names` check","problemTypes":[{"descriptions":[{"cweId":"CWE-200","lang":"en","description":"CWE-200: Exposure of Sensitive Information to an Unauthorized Actor","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-285","lang":"en","description":"CWE-285: Improper Authorization","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-639","lang":"en","description":"CWE-639: Authorization Bypass Through User-Controlled Key","type":"CWE"}]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"LOW","userInteraction":"NONE","vulnConfidentialityImpact":"LOW","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":5.3,"baseSeverity":"MEDIUM","vectorString":"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","version":"4.0"}}],"references":[{"name":"https://github.com/discourse/discourse/security/advisories/GHSA-5f9h-vp7v-7vq5","tags":["x_refsource_CONFIRM"],"url":"https://github.com/discourse/discourse/security/advisories/GHSA-5f9h-vp7v-7vq5"}],"affected":[{"vendor":"discourse","product":"discourse","versions":[{"version":">= 2026.1.0-latest, < 2026.1.2","status":"affected"},{"version":">= 2026.2.0-latest, < 2026.2.1","status":"affected"},{"version":"= 2026.3.0-latest","status":"affected"}]}],"providerMetadata":{"orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M","dateUpdated":"2026-03-20T03:10:43.213Z"},"descriptions":[{"lang":"en","value":"Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the ComposerController#mentions endpoint reveals hidden group membership to any authenticated user who can message the group. By supplying allowed_names referencing a hidden-membership group and probing arbitrary usernames, an attacker can infer membership based on whether user_reasons returns \"private\" for a given user. This bypasses group member-visibility controls. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. To work around this issue, restrict the messageable policy of any hidden-membership group to staff or group members only, so untrusted users cannot reach the vulnerable code path."}],"source":{"advisory":"GHSA-5f9h-vp7v-7vq5","discovery":"UNKNOWN"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-03-20T17:16:37.287787Z","id":"CVE-2026-31869","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-03-20T17:18:59.947Z"}}]}}