{"id":"CVE-2026-72721","state":"PUBLISHED","title":"Discourse: Onebox Domain Blocklist Bypass via Case-Sensitive Comparison","description":"Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, Onebox::DomainChecker.is_blocked? compares hostnames and SiteSetting.blocked_onebox_domains entries case-sensitively, allowing an attacker to bypass configured Onebox domain restrictions by changing character casing in a redirect target hostname. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.","publishedAt":"2026-08-10T15:48:30.548Z","updatedAt":"2026-08-10T16:59:07.554Z","severity":{"score":5.3,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["discourse discourse"],"affected":[{"vendor":"discourse","product":"discourse","versions":[{"version":"< 2026.1.6","status":"affected"},{"version":">= 2026.5.0-latest, < 2026.5.2","status":"affected"},{"version":">= 2026.6.0-latest, < 2026.6.1","status":"affected"},{"version":">= 2026.7.0-latest, < 2026.7.0","status":"affected"}]}],"references":["https://github.com/discourse/discourse/security/advisories/GHSA-3x7x-24rq-h5j6","https://github.com/discourse/discourse/pull/42091","https://github.com/discourse/discourse/pull/42092","https://github.com/discourse/discourse/pull/42093","https://github.com/discourse/discourse/pull/42094","https://github.com/discourse/discourse/commit/a3e10759fef47f03d450649bb51d9e84f4c68b8f","https://github.com/discourse/discourse/commit/c2eb6b0e5597d6f28f4be739b83300bc9c69e3cd","https://github.com/discourse/discourse/commit/caa615c371b1696982ee11ac8f3558f0f8ced584","https://github.com/discourse/discourse/commit/f503971d311b7b0dfdb751ee8cfd67e8cb99f5c5"],"weaknesses":["CWE-178"],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72721.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72721","state":"PUBLISHED","datePublished":"2026-08-10T15:48:30.548Z","dateUpdated":"2026-08-10T16:59:07.554Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-08-10T13:48:09.545Z"},"containers":{"cna":{"title":"Discourse: Onebox Domain Blocklist Bypass via Case-Sensitive Comparison","descriptions":[{"lang":"en","value":"Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, Onebox::DomainChecker.is_blocked? compares hostnames and SiteSetting.blocked_onebox_domains entries case-sensitively, allowing an attacker to bypass configured Onebox domain restrictions by changing character casing in a redirect target hostname. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0."}],"affected":[{"vendor":"discourse","product":"discourse","versions":[{"version":"< 2026.1.6","status":"affected"},{"version":">= 2026.5.0-latest, < 2026.5.2","status":"affected"},{"version":">= 2026.6.0-latest, < 2026.6.1","status":"affected"},{"version":">= 2026.7.0-latest, < 2026.7.0","status":"affected"}]}],"references":[{"url":"https://github.com/discourse/discourse/security/advisories/GHSA-3x7x-24rq-h5j6","name":"https://github.com/discourse/discourse/security/advisories/GHSA-3x7x-24rq-h5j6","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/discourse/discourse/pull/42091","name":"https://github.com/discourse/discourse/pull/42091","tags":["x_refsource_MISC"]},{"url":"https://github.com/discourse/discourse/pull/42092","name":"https://github.com/discourse/discourse/pull/42092","tags":["x_refsource_MISC"]},{"url":"https://github.com/discourse/discourse/pull/42093","name":"https://github.com/discourse/discourse/pull/42093","tags":["x_refsource_MISC"]},{"url":"https://github.com/discourse/discourse/pull/42094","name":"https://github.com/discourse/discourse/pull/42094","tags":["x_refsource_MISC"]},{"url":"https://github.com/discourse/discourse/commit/a3e10759fef47f03d450649bb51d9e84f4c68b8f","name":"https://github.com/discourse/discourse/commit/a3e10759fef47f03d450649bb51d9e84f4c68b8f","tags":["x_refsource_MISC"]},{"url":"https://github.com/discourse/discourse/commit/c2eb6b0e5597d6f28f4be739b83300bc9c69e3cd","name":"https://github.com/discourse/discourse/commit/c2eb6b0e5597d6f28f4be739b83300bc9c69e3cd","tags":["x_refsource_MISC"]},{"url":"https://github.com/discourse/discourse/commit/caa615c371b1696982ee11ac8f3558f0f8ced584","name":"https://github.com/discourse/discourse/commit/caa615c371b1696982ee11ac8f3558f0f8ced584","tags":["x_refsource_MISC"]},{"url":"https://github.com/discourse/discourse/commit/f503971d311b7b0dfdb751ee8cfd67e8cb99f5c5","name":"https://github.com/discourse/discourse/commit/f503971d311b7b0dfdb751ee8cfd67e8cb99f5c5","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":5.3,"baseSeverity":"MEDIUM","confidentialityImpact":"LOW","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-178","lang":"en","description":"CWE-178: Improper Handling of Case Sensitivity","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-08-10T15:48:30.548Z"},"source":{"advisory":"GHSA-3x7x-24rq-h5j6","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-10T16:58:55.983146Z","id":"CVE-2026-72721","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-10T16:59:07.554Z"}}]}}}