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CVE-2026-33557— Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication

Quick assessment

Affected
Apache Software Foundation Apache Kafka
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Apache Kafka是美国阿帕奇（Apache）基金会的一套开源的分布式流媒体平台。该平台能够获取实时数据，用于构建对数据流的变化进行实时反应的应用程序。 Apache Kafka 4.1.0版本和4.1.1版本存在安全漏洞，该漏洞源于默认JWT验证器未验证令牌签名、颁发者或受众，可能导致身份验证绕过。

AI Predicted 9.8 Difficulty: Trivial EPSS 0.93% · P60

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
Apache Software Foundation Apache Kafka 4.1.0≤ 4.1.1 affected
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I. Basic Information for CVE-2026-33557

Vulnerability Information
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Vulnerability Title
Apache Kafka: Missing JWT token validation in OAUTHBEARER authentication
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1285
Source: CVE Program / CVE List V5
Vulnerability Title
Apache Kafka 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Apache Kafka是美国阿帕奇（Apache）基金会的一套开源的分布式流媒体平台。该平台能够获取实时数据，用于构建对数据流的变化进行实时反应的应用程序。 Apache Kafka 4.1.0版本和4.1.1版本存在安全漏洞，该漏洞源于默认JWT验证器未验证令牌签名、颁发者或受众，可能导致身份验证绕过。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Apache Software Foundation Apache Kafka 4.1.0 ~ 4.1.1 -

II. Public POCs for CVE-2026-33557

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III. Intelligence Information for CVE-2026-33557

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Same Patch Batch · Apache Software Foundation · 2026-04-20 · 3 CVEs total

CVE-2026-33558 Apache Kafka, Apache Kafka Clients: Information Exposure Through Network Client Log Output
CVE-2025-66335 Apache Doris MCP Server: MCP SQL inject

IV. Related Vulnerabilities

Same product: Apache Kafka
Same vendor: Apache Software Foundation
Same weakness: CWE-1285

V. Comments for CVE-2026-33557

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