# CVE-2026-33557

## Summary

- **CVE ID:** CVE-2026-33557
- **Severity:** HIGH
- **CVSS Score:** 8.6 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L)
- **CWE:** CWE-1285
- **Published:** Apr 20, 2026
- **Last Modified:** Jul 15, 2026

## 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.

## Affected Products

- Apache Software Foundation — Apache Kafka (4.1.0)

## References

- [CNA](https://kafka.apache.org/cve-list)
- [CNA](https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h)
- [CVE](http://www.openwall.com/lists/oss-security/2026/04/17/2)
- [redhat-SADP](https://access.redhat.com/security/cve/CVE-2026-33557)
- [redhat-SADP](https://bugzilla.redhat.com/show_bug.cgi?id=2459739)
- [redhat-SADP](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33557.json)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.68%
- **EPSS Percentile:** 50.3

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._