{"id":"CVE-2026-33248","state":"PUBLISHED","title":"NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching","description":"NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.15 and 2.12.6, when using mTLS for client identity, with `verify_and_map` to derive a NATS identity from the client certificate's Subject DN, certain patterns of RDN would not be correctly enforced, allowing for authentication bypass. This does require a valid certificate from a CA already trusted for client certificates, and `DN` naming patterns which the NATS maintainers consider highly unlikely. So this is an unlikely attack. Nonetheless, administrators who have been very sophisticated in their `DN` construction patterns might conceivably be impacted. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, developers should review their CA issuing practices.","publishedAt":"2026-03-25T20:18:28.923Z","updatedAt":"2026-03-26T19:52:12.357Z","severity":{"score":4.2,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["nats-io nats-server"],"affected":[{"vendor":"nats-io","product":"nats-server","versions":[{"version":"< 2.11.15","status":"affected"},{"version":">= 2.12.0-RC.1, < 2.12.6","status":"affected"}]}],"references":["https://github.com/nats-io/nats-server/security/advisories/GHSA-3f24-pcvm-5jqc","https://advisories.nats.io/CVE/secnote-2026-13.txt"],"weaknesses":["CWE-287","CWE-295"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/33xxx/CVE-2026-33248.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-33248","state":"PUBLISHED","datePublished":"2026-03-25T20:18:28.923Z","dateUpdated":"2026-03-26T19:52:12.357Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-03-18T02:42:27.509Z"},"containers":{"cna":{"title":"NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching","descriptions":[{"lang":"en","value":"NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.15 and 2.12.6, when using mTLS for client identity, with `verify_and_map` to derive a NATS identity from the client certificate's Subject DN, certain patterns of RDN would not be correctly enforced, allowing for authentication bypass. This does require a valid certificate from a CA already trusted for client certificates, and `DN` naming patterns which the NATS maintainers consider highly unlikely. So this is an unlikely attack. Nonetheless, administrators who have been very sophisticated in their `DN` construction patterns might conceivably be impacted. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, developers should review their CA issuing practices."}],"affected":[{"vendor":"nats-io","product":"nats-server","versions":[{"version":"< 2.11.15","status":"affected"},{"version":">= 2.12.0-RC.1, < 2.12.6","status":"affected"}]}],"references":[{"url":"https://github.com/nats-io/nats-server/security/advisories/GHSA-3f24-pcvm-5jqc","name":"https://github.com/nats-io/nats-server/security/advisories/GHSA-3f24-pcvm-5jqc","tags":["x_refsource_CONFIRM"]},{"url":"https://advisories.nats.io/CVE/secnote-2026-13.txt","name":"https://advisories.nats.io/CVE/secnote-2026-13.txt","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":4.2,"baseSeverity":"MEDIUM","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-287","lang":"en","description":"CWE-287: Improper Authentication","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-295","lang":"en","description":"CWE-295: Improper Certificate Validation","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-03-25T20:18:28.923Z"},"source":{"advisory":"GHSA-3f24-pcvm-5jqc","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-33248","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-03-26T19:35:03.328665Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-03-26T19:52:12.357Z"}}]}}}