# CVE-2026-33557

> Vulnerability · severity: **CRITICAL** (CVSS 9.1).

## 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.

## Key facts

- **CVE ID:** CVE-2026-33557
- **Published:** 2026-04-20
- **CVSS severity:** CRITICAL
- **CVSS base score:** 9.1
- **CWE codes:** CWE-1285

## Affected products

- `apache:kafka`

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33557

## Citation

> AI Analytics. CVE-2026-33557. Retrieved 2026-07-19 from https://api.ai-analytics.org/cve/CVE-2026-33557. Derived from NIST NVD. Licensed CC0.

---

*[Dataset catalog](https://api.ai-analytics.org/datasets/) · [AI Analytics](https://api.ai-analytics.org/) · CC0 1.0*