CVE-2026-33557
Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication
At a glance
- Source
- NVD
- EPSS
- EPSS 0.90 % · percentile 59 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- apache
- NVD status
- Modified
Description
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.
Weaknesses (CWE)
References
- https://kafka.apache.org/cve-list
- https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h
- http://www.openwall.com/lists/oss-security/2026/04/17/2
- 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
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | CRITICAL 9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N | CISA-ADP |
| CVSS 3.1 | HIGH 8.6 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L | redhat-SADP |
| CVSS 3.1 | CRITICAL 9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N | NVD · 134c704f-9b21-4f2e-91b3-4a467353bcc0 (Secondary) |
| CVSS 3.1 | HIGH 8.6 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L | NVD · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c (Secondary) |
Advisories
- GHSA-28jg-cgg7-j4wc — Apache Kafka does not validate JWT tokens in its OAUTHBEARER authentication implementation
European references
- ENISA EUVD · EUVD-2026-23846
- GCVE · GCVE-0-2026-33557
CERT-FR advisories
- CERTFR-2026-AVI-0461 — Multiples vulnérabilités dans Apache Kafka · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:apache:kafka:*:*:*:*:*:*:*:*≥ 4.1.0 < 4.1.2
Affected products
| Product | Versions |
|---|---|
| Apache Software Foundation · Apache Kafka | affected 4.1.0 ≤ 4.1.1 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |