{"id":"CVE-2026-33557","aliases":["BIT-kafka-2026-33557","GHSA-28jg-cgg7-j4wc"],"url":"https://o3.security/vulnerability/CVE-2026-33557","summary":"Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication","details":"A possible security vulnerability has been identified in Apache Kafka.\n\nBy default, the broker property `sasl.oauthbearer.jwt.validator.class` is set to `org.apache.kafka.common.security.oauthbearer.DefaultJwtValidator`. It accepts any JWT token without validating its signature, issuer, or audience. An attacker can generate a JWT token from any issuer with the `preferred_username` set to any user, and the broker will accept it.\n\nWe advise the Kafka users using kafka v4.1.0 or v4.1.1 to set the config `sasl.oauthbearer.jwt.validator.class` to `org.apache.kafka.common.security.oauthbearer.BrokerJwtValidator` explicitly to avoid this vulnerability. Since Kafka v4.1.2 and v4.2.0 and later, the issue is fixed and will correctly validate the JWT token.","published":"2026-04-20T13:28:43.669Z","modified":"2026-08-12T03:51:25.689285569Z","cvss":{"score":9.1,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},"epss":{"score":0.00684,"percentile":0.49305,"asOf":"2026-08-12"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Maven","name":"org.apache.kafka:kafka-clients","fixedVersion":"4.1.2"}],"fix":null,"references":[{"type":"WEB","url":"http://www.openwall.com/lists/oss-security/2026/04/17/2"},{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33557.json"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-33557"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33557.json"},{"type":"ADVISORY","url":"https://kafka.apache.org/cve-list"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33557"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2459739"},{"type":"ARTICLE","url":"https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:25.689285569Z"}}