CVE-2026-33557
Apache Kafka does not validate JWT tokens in its OAUTHBEARER authentication implementation
Impact
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 packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| maven | org.apache.kafka:kafka-clients | >= 4.1.0, < 4.1.2 | 4.1.2 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Apache | Kafka | from 4.1.0 before 4.1.2 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-28jg-cgg7-j4wc
- https://nvd.nist.gov/vuln/detail/CVE-2026-33557
- https://kafka.apache.org/cve-list
- https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h
- http://www.openwall.com/lists/oss-security/2026/04/17/2
- https://github.com/apache/kafka/commit/01d8e7db8d08dbd538892b409457ea6bfcc2a422
- 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