CVE-2026-33557
possible security vulnerability has been identified in Apache Kafka.
Technology
Apache Kafka
CVSS Score
9.1 / 10.0
Affected Versions
>=4.1.0 <4.1.2
Upstream Fix
See upstream advisory
Published
April 20, 2026
OSSeva Coverage
Fixed upstream
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
Is your Apache Kafka deployment affected?
If you're running >=4.1.0 <4.1.2, you need this patch. Book a discovery call to get covered.