Executive brief
A race condition in the Apache Kafka Java client can cause messages to be silently sent to the wrong destination. This occurs when internal memory buffers are reused too quickly, potentially exposing sensitive data to unauthorized users or causing data corruption in downstream systems. Organizations using Kafka for data streaming should update their client libraries to prevent silent data misrouting.
Technical details
A race condition exists in the Apache Kafka Java producer client's buffer pool management (CWE-362). When a produce batch expires due to 'delivery.timeout.ms' while a network request is still in flight, the batch's ByteBuffer is prematurely deallocated and returned to the pool. If a subsequent batch reuses this buffer before the original request completes, the buffer contents may be corrupted or misrouted to an unintended topic. This occurs without reporting an error to the producer, leading to potential confidentiality breaches and data integrity issues. The vulnerability is reachable over the network but requires specific timing conditions (high complexity). Fixes are available in versions 3.9.2, 4.0.2, 4.1.2, and 4.2.0.
Affected products
- Apache kafka-clients >= 2.8.0, < 3.9.2; >= 4.0.0, < 4.0.2; >= 4.1.0, < 4.1.2
Timeline
- 2026-04-07: disclosed
- 2026-04-07: advisory
References
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- https://github.com/filipecamargos
- https://api.github.com/users/filipecamargos/gists%7B/gist_id%7D
- https://api.github.com/users/filipecamargos/repos
- https://avatars.githubusercontent.com/u/55758354?v=4
- https://api.github.com/users/filipecamargos/events%7B/privacy%7D