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GHSA-28JG-CGG7-J4WC

Vulnerability from github – Published: 2026-04-20 15:31 – Updated: 2026-04-24 15:29
VLAI
Summary
Apache Kafka does not validate JWT tokens in its OAUTHBEARER authentication implementation
Details

A 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.

Apache advises 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.

Severity
9.1 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.apache.kafka:kafka-clients"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.1.0"
            },
            {
              "fixed": "4.1.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-33557"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1285"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-24T15:29:31Z",
    "nvd_published_at": "2026-04-20T14:16:18Z",
    "severity": "CRITICAL"
  },
  "details": "A security vulnerability has been identified in Apache Kafka. By default, the broker property `sasl.oauthbearer.jwt.validator.class` is\u00a0set to `org.apache.kafka.common.security.oauthbearer.DefaultJwtValidator`. It accepts any JWT token without validating its\u00a0signature, issuer, or audience. An attacker can generate a JWT\u00a0token from any issuer with the `preferred_username` set to any user, and the broker will accept it.\n\nApache advises 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.",
  "id": "GHSA-28jg-cgg7-j4wc",
  "modified": "2026-04-24T15:29:32Z",
  "published": "2026-04-20T15:31:52Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33557"
    },
    {
      "type": "WEB",
      "url": "https://github.com/apache/kafka/commit/01d8e7db8d08dbd538892b409457ea6bfcc2a422"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/apache/kafka"
    },
    {
      "type": "WEB",
      "url": "https://kafka.apache.org/cve-list"
    },
    {
      "type": "WEB",
      "url": "https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/04/17/2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Apache Kafka does not validate JWT tokens in its OAUTHBEARER authentication implementation"
}



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