Report: Essential Guide: CVE-2026-33557 - Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication
CVE ID :CVE-2026-33557 Published : April 20, 2026, 2:16 p.m. | 40 minutes ago Description :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. Severity: 0.0 | NA Visit the link for more details, such as CVSS details, affected products, timeline, and more...