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A possible security vulnerability has been identified in Apache Kafka.
By 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.
We 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.

" } ], "value": "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." } ], "metrics": [ { "other": { "content": { "text": "important" }, "type": "Textual description of severity" } } ], "problemTypes": [ { "descriptions": [ { "cweId": "CWE-1285", "description": "CWE-1285 Improper Validation of Specified Index, Position, or Offset in Input", "lang": "en", "type": "CWE" } ] } ], "providerMetadata": { "orgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09", "shortName": "apache", "dateUpdated": "2026-04-20T13:28:43.669Z" }, "references": [ { "tags": [ "vendor-advisory" ], "url": "https://kafka.apache.org/cve-list" }, { "tags": [ "mailing-list" ], "url": "https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h" } ], "source": { "discovery": "UNKNOWN" }, "title": "Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication", "x_generator": { "engine": "Vulnogram 0.2.0" } }, "adp": [ { "title": "CVE Program Container", "references": [ { "url": 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