Threat Advisory

Apache Kafka Vulnerabilities Expose Authentication Bypass

Threat: Vulnerability
Targeted Region: Global
Targeted Sector: Technology & IT
Criticality: High
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EXECUTIVE SUMMARY:

Multiple security vulnerabilities have been identified in Apache Kafka, a cornerstone of high-performance data pipelines and mission-critical event streaming. The affected products are Apache Kafka with versions 4.1.0 through 4.1.1 and Apache Kafka Clients with versions 0.11.0 through 3.9.1, and 4.0.0. The overall vulnerability types include authentication bypass and sensitive data exposure. These vulnerabilities pose a significant business risk and impact, as they could allow unauthorized access to the stream and expose sensitive internal credentials or configuration data. This could lead to data breaches, loss of intellectual property, and damage to the organization's reputation.[/subscribe_to_unlock_form]

EXECUTIVE SUMMARY:

Multiple security vulnerabilities have been identified in Apache Kafka, a cornerstone of high-performance data pipelines and mission-critical event streaming. The affected products are Apache Kafka with versions 4.1.0 through 4.1.1 and Apache Kafka Clients with versions 0.11.0 through 3.9.1, and 4.0.0. The overall vulnerability types include authentication bypass and sensitive data exposure. These vulnerabilities pose a significant business risk and impact, as they could allow unauthorized access to the stream and expose sensitive internal credentials or configuration data. This could lead to data breaches, loss of intellectual property, and damage to the organization's reputation.[emaillocker id="1283"]

  • CVE-2026-33557 with a CVSS score of 9.8 – This vulnerability centers on a critical breakdown in authentication, allowing an attacker to generate their own JWT from any issuer, effectively granting them unauthorized access to the stream. An attacker can exploit this vulnerability by setting the preferred_username field to any user of their choosing and then convincing the broker to accept the token.
  • CVE-2026-33558 with a CVSS score of 5.9 – This vulnerability highlights a significant risk regarding sensitive data exposure due to the NetworkClient component outputting the full content of entire requests and responses directly into the system logs when set to the DEBUG log level. An attacker can exploit this vulnerability by accessing the system logs, which could contain sensitive internal credentials or configuration data.

Apache Kafka's authentication bypass and sensitive data exposure vulnerabilities pose a significant risk to organizations that rely on the platform for mission-critical event streaming and high-performance data pipelines. If exploited, these vulnerabilities could lead to data breaches, loss of intellectual property, and damage to the organization's reputation, resulting in significant financial losses and reputational harm. It is essential for administrators to take immediate action to mitigate these risks and prevent potential data breaches.

RECOMMENDATION:

We recommend you to update Apache Kafka to version 4.1.2 or 4.2.0.

REFERENCES:

The following
reports contain further technical details:
https://securityonline.info/apache-kafka-jwt-authentication-bypass-logging-vulnerabilities-2026/

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