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Release of Canton 3.5.2

Canton 3.5.2 has been released on June 03, 2026.

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Summary

This is a maintenance release that fixes an out of memory issue during synchronizer reconnect, addresses security vulnerabilities in the Canton docker base image, as well as minor improvements.

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Minor Improvements

• Updated the Docker base image to 1.0.8 to address vulnerabilities in Busybox: CVE-2025-46394, CVE-2025-60876.
• Fix sequencer subscription closing errors Timeout 9 seconds expired, but readers are still active in Task closing flushing direct-sequencer-subscription.
• Handle decoding of ContractId Void in PQS
• Improve caching of contract key lookups

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Deprecations

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Removal of synchronous processing on the mediator

The synchronous processing mode on the mediator has been removed in favor of the asynchronous one that offers better performance. Config path myMediator.config.asynchronous-processing has been deprecated as it is on by default now.

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Bugfixes

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(26-002, Medium): OOM from high memory usage after disconnecting and reconnecting from/to a synchronizer

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Issue Description

Because of the periodic time proof retrieval task (with interval minObservationDuration), the ConnectedSynchronizer instance cannot be garbage collected right away after a disconnect/reconnect from the synchronizer. This leads to higher memory consumption which can lead to OOMs.

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Affected Deployments

Participant nodes

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Affected Versions

All versions before 3.5.2

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Impact

High memory consumption and potentially OOM of the participant

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Symptom

The heap dump shows instances of the ConnectedSynchronizer from previously disconnected synchronizers. The stack of calls refers to PeriodicAcknowledgements, TimeProofRequestsSubmitterImpl, SynchronizerTimeTracker and finally Clock

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Workaround

Restart the participant.

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Likeliness

Sometimes

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Recommendation

Upgrade to 3.5.2

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Compatibility

The following Canton protocol versions are supported: Canton has been tested against the following versions of its dependencies: