Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication
Summary
| CVE | CVE-2026-33557 |
|---|---|
| State | PUBLISHED |
| Assigner | apache |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-04-20 14:16:18 UTC |
| Updated | 2026-06-30 03:18:41 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 9.1 CRITICAL from ADP
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS: 0.005810000 probability, percentile 0.434740000 (date 2026-07-02)
Problem Types: CWE-1285 | CWE-303 | CWE-1285 CWE-1285 Improper Validation of Specified Index, Position, or Offset in Input | CWE-303 Incorrect Implementation of Authentication Algorithm
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | ADP | DECLARED | 9.1 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
| 3.1 | ADP | CVSS | 8.6 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L |
| 3.1 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | Secondary | 9.1 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
| 3.1 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | Secondary | 8.6 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
HighIntegrity
HighAvailability
NoneCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33557.json | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | security.access.redhat.com | |
| access.redhat.com/security/cve/CVE-2026-33557 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h | [email protected] | lists.apache.org | Mitigation, Vendor Advisory |
| bugzilla.redhat.com/show_bug.cgi | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | bugzilla.redhat.com | |
| kafka.apache.org/cve-list | [email protected] | kafka.apache.org | Vendor Advisory |
| www.openwall.com/lists/oss-security/2026/04/17/2 | af854a3a-2127-422b-91ae-364da2661108 | www.openwall.com | Mailing List |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Павел Романов <[email protected]> (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| ADP | 2026-04-20T14:01:07.601Z | Reported to Red Hat. |
| ADP | 2026-04-20T13:28:43.669Z | Made public. |
There are currently no legacy QID mappings associated with this CVE.