CVE-2026-33557

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.

PUBLISHED Reserved 2026-03-23 | Published 2026-04-20 | Updated 2026-04-20 | Assigner apache

Problem types

CWE-1285 Improper Validation of Specified Index, Position, or Offset in Input

Product status

Credits

Павел Романов <promanov1994@gmail.com> finder

References

www.openwall.com/lists/oss-security/2026/04/17/2

kafka.apache.org/cve-list vendor-advisory

lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h mailing-list

cve.org (CVE-2026-33557)

nvd.nist.gov (CVE-2026-33557)

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