CVE-2026-33557

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.

CVSS v3 9.1 CRITICAL

9.1^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://kafka.apache.org/cve-list	Vendor Advisory
https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h	Mitigation Vendor Advisory
http://www.openwall.com/lists/oss-security/2026/04/17/2	Mailing List
https://access.redhat.com/security/cve/CVE-2026-33557
https://bugzilla.redhat.com/show_bug.cgi?id=2459739
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33557.json

Configurations

Configuration 1 (hide)

cpe:2.3:a:apache:kafka:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-04-20 14:16

Updated : 2026-07-15 02:20

NVD link : CVE-2026-33557

Mitre link : CVE-2026-33557

CVE.ORG link : CVE-2026-33557

JSON object : View

Products Affected

apache

kafka

CWE

CWE-1285

Improper Validation of Specified Index, Position, or Offset in Input

CWE-303

Incorrect Implementation of Authentication Algorithm

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"value": "A possible security vulnerability has been identified in Apache Kafka.\n\nBy 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\nWe 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."}], "lastModified": "2026-07-15T02:20:14.697", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:apache:kafka:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "5D700BB3-89AD-4488-8820-17C427E7983D", "versionEndExcluding": "4.1.2", "versionStartIncluding": "4.1.0"}], "operator": "OR"}]}], "sourceIdentifier": "security@apache.org"}