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CVE-2026-33557

CVE-2026-33557 · Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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.

CVSS 9.1 · Critical · EPSS 0.9%

Published
Updated

Stack: system

Affected products and versions

  • apache kafka

    Versions
    • ≥ 4.1.0, ≤ 4.1.1: Affected (semver)

    No fix published

  • kafka Ubuntu:Pro:18.04:LTS

    Versions
    • 2.2.0u2-0ubuntu3.1
    • 2.2.0u2-0ubuntu3.2
    • 2.2.2u1-0ubuntu1+esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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