{"id":"BIT-kafka-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.","aliases":["CVE-2026-33557","GHSA-28jg-cgg7-j4wc"],"modified":"2026-09-08T08:47:30.371242122Z","published":"2026-04-22T08:40:40.515Z","database_specific":{"severity":"Critical","cpes":["cpe:2.3:a:apache:kafka:*:*:*:*:*:maven:*:*"]},"references":[{"type":"DISCUSSION","url":"http://www.openwall.com/lists/oss-security/2026/04/17/2"},{"type":"ADVISORY","url":"https://kafka.apache.org/cve-list"},{"type":"ADVISORY","url":"https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h"},{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33557"},{"type":"WEB","url":"https://access.redhat.com/security/cve/CVE-2026-33557"},{"type":"WEB","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2459739"},{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33557.json"}],"affected":[{"package":{"name":"kafka","ecosystem":"Bitnami","purl":"pkg:bitnami/kafka"},"ranges":[{"type":"SEMVER","events":[{"introduced":"4.1.0"},{"fixed":"4.1.2"}]}],"database_specific":{"source":"https://github.com/bitnami/vulndb/tree/main/data/kafka/BIT-kafka-2026-33557.json"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"}]}],"schema_version":"1.9.0"}