SEPTEMBER 19, 2026
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Case File

CVE-2026-33557

CRITICAL · CVSS 9.1 EPSS 0.68%

Source: NVD + CISA KEV + EPSS (historical backfill) · Published 2026-04-20 · Last synced 2026-08-04

CyberRota Analysis

This is a critical severity vulnerability with a CVSS score of 9.1. It affects Apache.

CVE
CVE-2026-33557
Severity
CRITICAL
CVSS
9.1
EPSS
0.68%
Apache

Original NVD 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.

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