by Kastro
Paper/Archive/CVE-2026-33557

CVE-2026-33557

Apache Software Foundation Apache Kafka — Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication

EPSS 0.9%CVSS 9.1
critical.is priorityof 100
39
CVSS 9.1 (ADP)9.1 / 10 × 3027.3Not in CISA KEV+300.0EPSS percentile 59.6.596 × 2011.9No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
Apache Kafka4.1.0 – 4.1.1–CNA
OpenShift Serverlesssee advisory–redhat-SADP
OpenShift Serverlesssee advisory–redhat-SADP
Red Hat build of Apache Camel 4 for Quarkus 3see advisory–redhat-SADP
Red Hat build of Apache Camel for Spring Boot 4see advisory–redhat-SADP
Red Hat build of Apache Camel for Spring Boot 4see advisory–redhat-SADP
Red Hat build of Apicurio Registry 2see advisory–redhat-SADP
Red Hat build of Apicurio Registry 3see advisory–redhat-SADP
Red Hat build of Debezium 2see advisory–redhat-SADP
Red Hat build of Debezium 3see advisory–redhat-SADP
Red Hat build of Quarkussee advisory–redhat-SADP
Red Hat Data Grid 8see advisory–redhat-SADP

Scores by source

CISA ADP9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
redhat-SADP (CNA)8.6CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: partial

References

advisorykafka.apache.org/cve-listreflists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953hrefopenwall.com/lists/oss-security/2026/04/17/2refaccess.redhat.com/security/cve/CVE-2026-33557refbugzilla.redhat.com/show_bug.cgi?id=2459739refsecurity.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33557.json