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CVE

CVE-2026-33557

Apache Kafka does not validate JWT tokens in its OAUTHBEARER authentication implementation
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CVE

CVE-2026-33557

Apache Kafka does not validate JWT tokens in its OAUTHBEARER authentication implementation

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.

Package Versions Affected

Package Version
patch Availability
No items found.

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CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
9.1
-
3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
C
H
U
0
-
3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
C
H
U
-

Related Resources

No items found.

References

https://nvd.nist.gov/vuln/detail/CVE-2026-33557, https://github.com/apache/kafka/commit/01d8e7db8d08dbd538892b409457ea6bfcc2a422, https://github.com/apache/kafka, https://kafka.apache.org/cve-list, https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h, http://www.openwall.com/lists/oss-security/2026/04/17/2

Severity

9.1

CVSS Score
0
10

Basic Information

Ecosystem
Base CVSS
9.1
EPSS Probability
0.002%
EPSS Percentile
0.41988%
Introduced Version
4.1.0,0
Fix Available
4.1.2,2.8.0-r7

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