{"id":"CVE-2026-33217","aliases":["BIT-nats-2026-33217","GHSA-jxxm-27vp-c3m5","GO-2026-4834"],"url":"https://o3.security/vulnerability/CVE-2026-33217","summary":"NATS allows MQTT clients to bypass ACL checks","details":"### Background\n\nNATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing.\n\nThe nats-server provides an MQTT client interface.\n\n### Problem Description\n\nWhen using ACLs on message subjects, these ACLs were not applied in the `$MQTT.>` namespace, allowing MQTT clients to bypass ACL checks for MQTT subjects.\n\n### Affected Versions\n\nAny version before v2.12.6 or v2.11.15\n\n### Workarounds\n\nNone.","published":"2026-03-25T19:43:40.969Z","modified":"2026-10-28T02:30:56.654292001Z","cvss":{"score":7.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N"},"epss":{"score":0.00259,"percentile":0.1787,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/nats-io/nats-server/v2","fixedVersion":"2.11.15"},{"ecosystem":"Go","name":"github.com/nats-io/nats-server/v2","fixedVersion":"2.12.6"},{"ecosystem":"Go","name":"github.com/nats-io/nats-server","fixedVersion":null}],"fix":null,"references":[{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33217.json"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:21769"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:22347"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:23345"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-33217"},{"type":"ADVISORY","url":"https://advisories.nats.io/CVE/secnote-2026-07.txt"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33217.json"},{"type":"ADVISORY","url":"https://github.com/nats-io/nats-server/security/advisories/GHSA-jxxm-27vp-c3m5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33217"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2451446"},{"type":"PACKAGE","url":"https://github.com/nats-io/nats-server"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:30:56.654292001Z"}}