Apache Kafka does not validate JWT tokens in its OAUTHBEARER authentication implementation

緊急 9.1CVE-2026-33557 · BIT-kafka-2026-33557 · GHSA-28jg-cgg7-j4wc · 20/04/2026 公開 · 26/10/2026 更新

要点

CVE-2026-33557 は org.apache.kafka:kafka-clients, kafka (apache) に影響する深刻度「緊急」 (CVSS 9.1) の脆弱性です。
今後30日間に悪用される確率（EPSS）：0.90%（全脆弱性の 59.6% より高い）。
対処：4.1.2 以降に更新してください。

パッケージ	影響を受けるバージョン	修正済みバージョン
org.apache.kafka:kafka-clients Maven	`≥ 4.1.0, < 4.1.2`	`4.1.2`
kafka apache	`≥ 4.1.0, < 4.1.2`	`4.1.2`

概要

A 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.

Apache advises 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.

NVD の説明

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.