Deserialization of Untrusted Data vulnerability in Apache Camel.
This issue affects Apache Camel: from 4.0.0 before 4.18.5, from 4.19.0 before 4.22.1.
The camel-hazelcast component applies a default Hazelcast JavaSerializationFilterConfig to the instances it creates from its own configuration, a protection introduced by CVE-2026-43865. That change did not reach two of the configuration paths Camel builds itself, so those paths continued to create Hazelcast instances whose Java deserialization is unrestricted. ReplicatedHazelcastAggregationRepository extends HazelcastAggregationRepository but overrides doStart() without calling super.doStart(), keeping its own copy of the bootstrap block, and therefore never received the filter: a route using it without supplying a hazelcastInstance starts a Hazelcast member that deserializes values read from the backing ReplicatedMap with no class restriction. HazelcastDefaultComponent#getOrCreateHzClientInstance() builds its own ClientConfig when hazelcastMode=client is selected and neither a referenced ClientConfig nor hazelcastConfigUri is supplied, and likewise applied no filter, so client-mode endpoints behaved differently from node-mode endpoints for an otherwise identical configuration. In both cases an attacker able to publish into the Hazelcast cluster that the affected instance is attached to can cause a serialized Java object of their choosing to be deserialized inside Hazelcast's own serialization layer, before Camel processes the exchange, resulting in remote code execution. Hazelcast clusters have neither authentication nor TLS enabled by default. Selecting client mode is a topology choice rather than a security option, so neither path required the deployment to opt in to unsafe behaviour.
Users are recommended to upgrade to version 4.23.0, which fixes the issue. If users are on the 4.22.x releases stream, then they are suggested to upgrade to 4.22.1. If users are on the 4.18.x releases stream, then they are suggested to upgrade to 4.18.5. The 4.14.x releases stream and earlier reached end of life before this issue was resolved and will not receive a fix, so deployments on those lines must move to a supported release. For deployments that cannot upgrade immediately, supply an explicit Hazelcast configuration carrying a JavaSerializationFilterConfig, or inject a pre-built HazelcastInstance, since a user-supplied configuration is never overwritten by Camel. Alternatively set the JVM-wide filter -Djdk.serialFilter=!java.net.;java.;javax.;org.apache.camel.;!* and enable Hazelcast cluster authentication and TLS to restrict who can reach the cluster.