CVE-2026-107726: Hazelcast: Arbitrary member memory access by low-privileged client
Impact
A flaw has been found in Hazelcast Enterprise Edition and Community Edition, which would allow a low-privileged malicious client to read arbitrary data in memory from any cluster member (including Java heap memory, off-heap data, and JVM process address space). Additionally, such a client may be able to cause one or more cluster members to crash, or in some Enterprise Edition configurations also corrupt memory contents, potentially leading to remote code execution. Both slim and full distributions are affected.
Patches
Enterprise customers should upgrade to a fixed version of Hazelcast Enterprise Edition: 5.7.0 5.6.1 5.5.10 5.4.5 Customers with extended support contracts should contact Hazelcast Support for information on patches for older versions.
Community Edition users should upgrade to version 5.7.0.
Hazelcast also recommends all customers follow the advice in our Security Hardening guide, including:
Ensure Hazelcast Security is enabled and client authorization is enforced. Define an explicit allowlist for zero config Compact serialization. Avoid deploying clients on internet-facing non-secure networks or non-secure hosts. Ensure your Hazelcast cluster is appropriately protected by firewall rules. Disable any features you are not using.
Workarounds If you cannot update to a fixed version immediately, restrict cluster access to trusted clients only and ensure clients are hardened against compromise.
References
Security Advisory on the Hazelcast Support Portal
Other sources
Hazelcast is a unified real-time data platform combining stream processing with a fast data store. Prior to 5.4.5, 5.5.10, and 5.6.1, improper validation of data supplied by a malicious client able to connect to a cluster allows arbitrary reads from a cluster member's Java heap, off-heap data, and JVM process address space. The same flaw can crash cluster members and, in some Hazelcast Enterprise Edition configurations, corrupt memory with possible arbitrary code execution. Both slim and full distributions are affected. This issue is fixed in versions 5.4.5, 5.5.10, 5.6.1, and 5.7.0.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
maven/com.hazelcast:hazelcastto a version that resolves this vulnerability.Fixed in 5.7.0 - Upgrade
Upgrade
Hazelcastto a version that resolves this vulnerability.Fixed in 5.4.5 - Upgrade
Upgrade
Hazelcastto a version that resolves this vulnerability.Fixed in 5.5.10 - Upgrade
Upgrade
Hazelcastto a version that resolves this vulnerability.Fixed in 5.6.1 - Upgrade
Upgrade
Hazelcast Community Editionto a version that resolves this vulnerability.Fixed in 5.7.0 - Configuration
Define an explicit allowlist for zero config Compact serialization.
Hazelcast zero config Compact serialization allowlist = explicit allowlist - Configuration
Enable Hazelcast Security.
Hazelcast Hazelcast Security = enabled - Configuration
Enforce client authorization.
Hazelcast client authorization = enforced - Configuration
Disable features that are not being used.
Hazelcast unused features = disabled - Compensating control
Ensure the Hazelcast cluster is protected by appropriate firewall rules and restrict cluster access to trusted clients only.
- Compensating control
Avoid deploying clients on internet-facing non-secure networks or non-secure hosts, and ensure clients are hardened against compromise.
Event History
Frequently Asked Questions
Which deployments are affected?
Hazelcast versions before 5.4.5, 5.5.10, and 5.6.1 are affected. Both slim and full distributions are impacted, and the issue applies when a malicious client can connect to the cluster.
What access does an attacker need?
An attacker needs the ability to connect as a client to a Hazelcast cluster. The client is described as low-privileged; no member-level privileges are stated as necessary.
What could exploitation do?
A malicious client can read arbitrary memory from a cluster member, including the Java heap, off-heap data, and the JVM process address space. The flaw can also crash cluster members and may permit memory corruption with possible arbitrary code execution in some Hazelcast Enterprise Edition configurations.
Which versions contain the fix?
The issue is fixed in Hazelcast 5.4.5, 5.5.10, 5.6.1, and 5.7.0.