CVE-2026-105927

published 2026-10-21

CVE-2026-105927: The Apache Pulsar WebSocket service allows a WebSocket consumer to configure a dead letter policy through query parameters of the consumer endpoint, including…

Priority P4 20 low 2.3 CVSS 4.0

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The Apache Pulsar WebSocket service allows a WebSocket consumer to configure a dead letter policy through query parameters of the consumer endpoint, including the deadLetterTopic parameter that names the topic to which messages are written after the maximum number of redeliveries is exceeded. When authorization is enabled, the WebSocket service checks only that the connecting user holds the CONSUME permission on the subscribed topic. It does not check whether the user holds the PRODUCE permission on the topic named in deadLetterTopic. The dead letter messages are then written by the WebSocket service using its own broker client identity rather than the identity of the connecting user.

As a result, an authenticated user who holds the CONSUME permission on at least one topic can cause messages to be written to a topic of their choosing in any existing namespace, including namespaces belonging to other tenants, provided the role used by the WebSocket service to connect to the brokers is authorized to produce to that topic and the topic accepts a producer that registers no schema. The dead letter producer created by the WebSocket service registers no schema, so it is rejected when the target topic has a schema and schema validation is enforced for that topic or its namespace; this setting is not enabled by default. The same user is refused when attempting to produce to that topic directly. Where automatic topic creation is enabled, which is the default, the named topic is created if it does not already exist. The issue can only be triggered when the WebSocket service is enabled, either in the broker (webSocketServiceEnabled, which is disabled by default) or as a standalone WebSocket proxy.

The impact is unauthorized injection of messages into topics the user is not permitted to produce to. The user can determine the content of the injected messages when they also control the messages on the subscribed topic. The issue does not allow reading, modifying or deleting exis

Affected

2 ranges

Vendor	Product	Version range	Fixed in
apache_software_foundation	apache_pulsar	>= 2.3.0 < 4.0.14	4.0.14
apache_software_foundation	apache_pulsar	>= 4.1.0 < 4.2.5	4.2.5

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CWE-863