Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication

{
  "id": "d683488ff234517f24bfd6440714b3dc41f6a9502c2177335cf6027d1ed6f18c",
  "url": "https://osv.dev/vulnerability/CVE-2026-33557",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication",
    "summary": "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.",
    "evidence": "osv:CVE-2026-33557",
    "products": [],
    "severity": "critical",
    "structured": {
      "id": "CVE-2026-33557",
      "aliases": [
        "BIT-kafka-2026-33557",
        "CVE-2026-33557",
        "GHSA-28jg-cgg7-j4wc"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/apache/kafka",
              "type": "GIT",
              "events": [
                {
                  "introduced": "13f70256db3c994c590e5d262a7cc50b9e973204"
                },
                {
                  "fixed": "c82fd9b934b4c1e6fa799e3f1dcc8f08d997740c"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:apache:kafka:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "4.1.0"
                      },
                      {
                        "fixed": "4.1.2"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "4.1.1-rc2",
            "4.1.1",
            "4.1.1-rc1",
            "4.1.0-rc3",
            "4.1.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33557.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:27.270900661Z",
      "provider": "osv",
      "references": [
        "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33557.json",
        "https://access.redhat.com/security/cve/CVE-2026-33557",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33557.json",
        "https://kafka.apache.org/cve-list",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-33557",
        "https://bugzilla.redhat.com/show_bug.cgi?id=2459739",
        "https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-1285"
        ],
        "cna_assigner": "apache",
        "unresolved_ranges": [
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "4.1.0"
                  },
                  {
                    "last_affected": "4.1.1"
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StandardRange"
              }
            ]
          }
        ],
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33557.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-33557",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 493986,
  "published_at": "2026-04-20T13:28:43.669+00:00"
}