CVE-2026-107726: Hazelcast allows arbitrary member memory access by low-privileged client

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.4%, percentile 31: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 31% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes com.hazelcast:hazelcast (Maven) = 5.6.0, fixed in 5.7.0; com.hazelcast:hazelcast (Maven) >= 5.5.0, < 5.5.10, fixed in 5.7.0; com.hazelcast:hazelcast (Maven) < 5.4.5, fixed in 5.7.0. Check your lockfile, including transitive dependencies.

What it is

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.

From the GitHub advisory

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.

Weakness type: CWE-20.

Product: com.hazelcast:hazelcast (Maven) · Assigned by: GitHub_M · Published: 2026-10-08

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.38% probability of exploitation activity in the next 30 days; percentile 31.

Timeline

• 2026-10-08 — CVE record published by GitHub_M
• 2026-10-08 — GitHub-reviewed advisory GHSA-6v25-8wq6-xq4j published (critical)
• 2026-10-09 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-6v25-8wq6-xq4j github.com
2. CVE.org record CVE-2026-107726 cve.org
3. NVD entry CVE-2026-107726 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. docs.hazelcast.com docs.hazelcast.com
4. docs.hazelcast.com docs.hazelcast.com
5. github.com github.com

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