{"id":"CVE-2026-33557","published":"2026-04-20T13:28:43Z","modified":"2026-07-15T01:06:14Z","title":"Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication","vendor":"Apache","product":"Apache Kafka","tier":"tail","description":{"text":"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.","provenance":"source","from":"CVE.org"},"cvss":{"score":9.1,"severity":"CRITICAL","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","provenance":"source","from":"CISA ADP Vulnrichment"},"epss":{"score":0.00897,"percentile":0.59462,"provenance":"source"},"cwes":[{"id":"CWE-1285","name":"Improper Validation of Specified Index, Position, or Offset in Input"},{"id":"CWE-303","name":"Incorrect Implementation of Authentication Algorithm"}],"references":[{"url":"https://kafka.apache.org/cve-list","tags":["vendor-advisory"]},{"url":"https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h","tags":["mailing-list"]},{"url":"http://www.openwall.com/lists/oss-security/2026/04/17/2","tags":[]},{"url":"https://access.redhat.com/security/cve/CVE-2026-33557","tags":["vdb-entry","x_refsource_REDHAT"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2459739","tags":["issue-tracking","x_refsource_REDHAT"]},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33557.json","tags":["x_sadp-csaf-vex"]}],"priority":{"score":18.3,"factors":[{"name":"EPSS percentile","points":11.89},{"name":"CVSS severity","points":6.37}]},"vendorSlug":"apache","affectedVersions":[{"vendor":"Apache Software Foundation","product":"Apache Kafka","versions":[">= 4.1.0, <= 4.1.1"]}],"affected":[{"ecosystem":"Maven","package":"org.apache.kafka:kafka-clients","vulnerableRanges":[">=4.1.0, <4.1.2"],"patched":["4.1.2"],"from":["GHSA-28jg-cgg7-j4wc"],"provenance":"source"}],"euvd":{"id":"EUVD-2026-23846","exploited":false,"provenance":"source"}}