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CVE-2026-33557

9.1 · CRITICAL

A possible security vulnerability has been identified in Apache Kafka.

Published Apr 20, 2026CWE-1285EPSS 0.93%

Overview

CVE-2026-33557 is a critical-severity vulnerability. It was published on April 20, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refkafka.apache.org/cve-listReflists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953hRefwww.openwall.com/lists/oss-security/2026/04/17/2Refaccess.redhat.com/security/cve/CVE-2026-33557Refbugzilla.redhat.com/show_bug.cgi?id=2459739Refsecurity.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33557.json

How CyberStrike helps

Frequently asked questions

What is CVE-2026-33557?

CVE-2026-33557 is a critical-severity vulnerability. It was published on April 20, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-33557?

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-33557?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-33557?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-33557 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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