Authorization Bypass in Apache Pulsar's Shadow Topics Feature

CVE-2026-105937

What is CVE-2026-105937?

The Apache Pulsar shadow topics feature can be exploited due to insufficient authorization checks, allowing authenticated users to link a topic in their tenant to a persistent topic in any other tenant. This occurs when users create or update topics, leveraging the PULSAR.SHADOW_SOURCE property without requiring permissions on the source topic. As a result, these users can access retained messages from the source topic, potentially leading to unauthorized data exposure. Furthermore, shadow topics can manipulate the source topic's retention settings, risking unintended data deletion. Recommended actions include upgrading to fixed versions where shadow topics are disabled by default, thereby enhancing overall security.

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