cvedb.io
CVE-2026-33557
CRITICAL · CVSS 9.1
EPSS exploitation probability: 0%
Published 2026-04-20T14:16:18.780 · Last modified 2026-06-30T03:18:41.357

Summary

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.

Affected products

apache — kafka

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References

This product uses data from the NVD API but is not endorsed or certified by the NVD. Informational only; not professional security advice.