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.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NWeakness enumeration
Affected software
| Vendor | Product | Versions |
|---|---|---|
| Apache Software Foundation | Apache Kafka | >= 4.1.0, <= 4.1.1 |
| Red Hat | OpenShift Serverless | — |
| Red Hat | OpenShift Serverless | — |
| Red Hat | Red Hat build of Apache Camel 4 for Quarkus 3 | — |
| Red Hat | Red Hat build of Apache Camel for Spring Boot 4 | — |
| Red Hat | Red Hat build of Apache Camel for Spring Boot 4 | — |
| Red Hat | Red Hat build of Apicurio Registry 2 | — |
| Red Hat | Red Hat build of Apicurio Registry 3 | — |
| Red Hat | Red Hat build of Debezium 2 | — |
| Red Hat | Red Hat build of Debezium 3 | — |
| Red Hat | Red Hat build of Quarkus | — |
| Red Hat | Red Hat Data Grid 8 | — |
| Red Hat | Red Hat Data Grid 8 | — |
| Red Hat | Red Hat Enterprise Linux 8 | — |
| Red Hat | Red Hat Enterprise Linux 9 | — |
| Red Hat | Red Hat Fuse 7 | — |
| Red Hat | Red Hat Fuse 7 | — |
| Red Hat | Red Hat JBoss Enterprise Application Platform 7 | — |
| Red Hat | Red Hat JBoss Enterprise Application Platform 7 | — |
| Red Hat | Red Hat JBoss Enterprise Application Platform 8 | — |
| Red Hat | Red Hat JBoss Enterprise Application Platform 8 | — |
| Red Hat | Red Hat JBoss Enterprise Application Platform Expansion Pack | — |
| Red Hat | Red Hat JBoss Enterprise Application Platform Expansion Pack | — |
| Red Hat | Red Hat Process Automation 7 | — |
| Red Hat | streams for Apache Kafka 2 | — |
| Red Hat | streams for Apache Kafka 2 | — |
| Red Hat | streams for Apache Kafka 3 | — |
| Red Hat | streams for Apache Kafka 3 | — |
References
- https://kafka.apache.org/cve-listVendor Advisory
- https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953hMitigation, Vendor Advisory
- http://www.openwall.com/lists/oss-security/2026/04/17/2Mailing List
- https://access.redhat.com/security/cve/CVE-2026-33557
- https://bugzilla.redhat.com/show_bug.cgi?id=2459739
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33557.json
Timeline
- Published
- Apr 20, 2026
- Last modified
- Oct 26, 2026
- NVD status
- Modified