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Critical

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

  • Disclosed: 20.04.2026
  • Updated: 11.10.2026 13:20

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.

Affected software

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PlatformPackageVulnerable versionsFixed in
Java / Kotlin (Maven) org.apache.kafka:kafka-clients >= 4.1.0, < 4.1.2 4.1.2

References

CVSS score 9.1/10
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness (CWE)
CWE-1285
Platform
Java / Kotlin (Maven)
Package
org.apache.kafka:kafka-clients
Disclosed
20.04.2026
Updated
11.10.2026 13:20

Sources and licenses

OSV / GitHub Advisory Database - GHSA-28jg-cgg7-j4wc - CC BY 4.0

Vulnerability history: org.apache.kafka:kafka-clients

All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.

Total entries
7
First → latest
09.2021 04.2026
Without a fix
0
Exploited in attacks
0

Severity breakdown

  • Critical 1
  • High 1
  • Medium 5

Disclosures per year

  1. Apache Kafka exposes sensitive information in its DEBUG logs
    Medium · 5.3 CVE-2026-33558 >= 0.11.0, < 3.9.2, >= 4.0.0, < 4.0.1 3.9.2, 4.0.1
  2. Apache Kafka does not validate JWT tokens in its OAUTHBEARER authentication implementation this entry
    Critical · 9.1 CVE-2026-33557 >= 4.1.0, < 4.1.2 4.1.2
  3. Apache Kafka Clients: Kafka Producer Message Corruption and Misrouting via Buffer Pool Race Condition
    High · 8.7 CVE-2026-35554 >= 2.8.0, < 3.9.2, >= 4.0.0, < 4.0.2, >= 4.1.0, < 4.1.2 3.9.2, 4.0.2, 4.1.2
  4. Apache Kafka Client Arbitrary File Read and Server Side Request Forgery Vulnerability
    Medium · 7.5 CVE-2025-27817 >= 3.1.0, < 3.9.1 3.9.1
  5. Apache Kafka Clients: Privilege escalation to filesystem read-access via automatic ConfigProvider
    Medium · 6.5 CVE-2024-31141 >= 2.3.0, < 3.7.1 3.7.1
  6. Improper Authentication in Apache Kafka
    Medium · 6.8 CVE-2017-12610 >= 0.10.0.0, < 0.10.2.2, >= 0.11.0.0, < 0.11.0.2 0.10.2.2, 0.11.0.2
  7. Observable Discrepancy in Apache Kafka
    Medium · 5.9 CVE-2021-38153 >= 2.0.0, < 2.6.3, >= 2.7.0, < 2.7.2, >= 2.8.0, < 2.8.1 2.6.3, 2.7.2, 2.8.1

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