CVE-2026-33557
kafka: Apache Kafka: Authentication bypass via improper JWT validation
Severity
ImportantRed Hat Product Security
CVSS 3.1
Review impact separately from score.
Published · April 20, 2026
Updated · November 5, 2026
Description
A flaw was found in Apache Kafka. By default, the sasl.oauthbearer.jwt.validator.class property is set to org.apache.kafka.common.security.oauthbearer.DefaultJwtValidator, which does not validate JSON Web Token (JWT) signatures, issuers, or audiences. A remote attacker can exploit this by crafting a malicious JWT token with an arbitrary preferred_username, leading to an authentication bypass and unauthorized access to the Kafka broker.
CVSS score applicability
The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.
Mitigation
No mitigation is specified in collected source.
CVSS / CWE
CVSS 3.1 · 8.6CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
CWE-303 · Incorrect Implementation of Authentication Algorithm