CVE-2026-33557

CRITICAL EPSS 39.0%
Published Apr 20, 20262mo ago · Modified Jun 17, 20261w ago
9.1 CVSS 3.1
Critical
Find Similar
Published Apr 20, 2026 2mo ago
Last Modified Jun 17, 2026 1w ago

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.

CVSS Details

Base Score
9.1
Exploitability
3.9
Impact
5.2
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality High
Integrity High
Availability None

Threat Intelligence

EPSS Exploit Probability
39.0% percentile
Exploit & Patch Status
No Known Exploit
No Patch Available

Weaknesses 1

CWE-1285

Affected Products 1

VendorProductVersionRange
apachekafka*≥4.1.0  –  <4.1.2

References 3

  • openwall.com http://www.openwall.com/lists/oss-security/2026/04/17/2
    Mailing List
  • kafka.apache.org https://kafka.apache.org/cve-list
    Vendor Advisory
  • lists.apache.org https://lists.apache.org/thread/v57o00hm6yszdpdnvqx2ss4561yh953h
    MitigationVendor Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.