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Fencer Vulns
critical 9.1

CVE-2026-33557 in the critical feed json

Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication

published 2026-04-20 6 mo ago modified 2026-10-26 13 d ago also BIT-kafka-2026-33557 , EUVD-2026-23846 , GHSA-28jg-cgg7-j4wc

cvss
9.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.9%
EPSS 0.9% chance of exploitation in 30 days, percentile 59%
public exploits
0
none known

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.

Patch / fix

  • maven org.apache.kafka:kafka-clients 4.1.2
  • bitnami kafka 4.1.2
  • apache kafka 4.1.2
  • org.apache.kafka kafka 4.1.2

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-33557 updated cvss 8.6

kafka: Apache Kafka: Authentication bypass via improper JWT validation

  • Red Hat build of Debezium 3 connect-api
    affected: no fix planned “Will not fix”
  • Red Hat streams for Apache Kafka 3 connect-api, kafka-clients
    affected: no fix available
  • Red Hat OpenShift Serverless openshift-serverless-1/kn-ekb-receiver-rhel9, openshift-serverless-1/kn-ekb-dispatcher-rhel9 Red Hat build of Apache Camel 4 for Quarkus 3 kafka-clients Red Hat build of Apache Camel for Spring Boot 4 connect-api, kafka-clients Red Hat build of Apicurio Registry 2 connect-api Red Hat build of Apicurio Registry 3 connect-api Red Hat build of Debezium 2 connect-api
    +10 more products
    Red Hat build of Quarkus kafka-clients Red Hat Data Grid 8 connect-api, kafka-clients Red Hat Enterprise Linux 8 log4j, log4j-jcl, log4j-web, log4j-slf4j Red Hat Enterprise Linux 9 log4j, log4j-jcl, log4j-slf4j Red Hat Fuse 7 connect-api, kafka-clients Red Hat JBoss Enterprise Application Platform 7 connect-api, kafka-clients Red Hat JBoss Enterprise Application Platform 8 connect-api, kafka-clients Red Hat JBoss Enterprise Application Platform Expansion Pack connect-api, kafka-clients Red Hat Process Automation 7 kafka-clients Red Hat streams for Apache Kafka 2 connect-api, kafka-clients
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.90% chance of exploitation in the next 30 days, higher than 59% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CISA ADP 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
GitHub 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CNA 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CNA 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
OSV 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
maven org.apache.kafka:kafka-clients
>=4.1.0, <4.1.2
4.1.2
bitnami kafka
>=4.1.0, <4.1.2
4.1.2

Affected products

  • Apache Software Foundation Apache Kafka
  • Red Hat OpenShift Serverless
  • Red Hat Red Hat build of Apache Camel 4 for Quarkus 3
  • Red Hat Red Hat build of Apache Camel for Spring Boot 4
  • Red Hat Red Hat build of Apicurio Registry 2
  • Red Hat Red Hat build of Apicurio Registry 3
  • Red Hat Red Hat build of Debezium 2
  • Red Hat Red Hat build of Debezium 3
  • Red Hat Red Hat build of Quarkus
  • Red Hat Red Hat Data Grid 8
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Fuse 7
  • Red Hat Red Hat JBoss Enterprise Application Platform 7
  • Red Hat Red Hat JBoss Enterprise Application Platform 8
  • Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack
  • Red Hat Red Hat Process Automation 7
  • Red Hat streams for Apache Kafka 2
  • Red Hat streams for Apache Kafka 3

Classification

Weakness
  • CWE-1285 Improper Validation of Specified Index, Position, or Offset in Input
  • CWE-303 Incorrect Implementation of Authentication Algorithm
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.