# CVE-2026-100302: Apache ZooKeeper denial of service in multiRead handler

Source: https://junglewise.ai/threats/cve-2026-100302-allocation-of-resources-without-limits-or-throttling-in-the  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-04. Updated: 2026-11-04  
License: CC BY 4.0 with a link back

CVE-2026-100302 · Severity: info · Published 2026-11-04

Apache ZooKeeper is a distributed coordination service used by many enterprise applications to manage configuration and state. A remote attacker can send a specially crafted multiRead request that forces the server to allocate excessive memory, exhausting the Java heap and crashing the server. This results in denial of service, disrupting all applications that depend on ZooKeeper for coordination and failover.

Technologies: [Apache Zookeeper](https://junglewise.ai/threats/technologies/zookeeper). Vendors: [Apache](https://junglewise.ai/threats/vendors/apache).

## Quick answers

**Is CVE-2026-100302 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-100302 being exploited in the wild.

**How severe is CVE-2026-100302?** Informational severity, published 4 November 2026.

**Which products and versions are affected?** Apache Zookeeper 3.7.0 through 3.9.6.

**Is there a fix for CVE-2026-100302?** Yes: fixed in 3.9.7. Until then: Restrict network access to ZooKeeper ports to only authorized clients and internal services. Configure firewall rules to limit connections to trusted hosts until upgrading to version 3.9.7. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-100302 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-100302?** Check whether you run Apache Zookeeper at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 3.9.7

Restrict network access to ZooKeeper ports to only authorized clients and internal services. Configure firewall rules to limit connections to trusted hosts until upgrading to version 3.9.7.

## Technical details

The multiRead request handler in ZooKeeper lacks limits on the number of bundled read operations and the cumulative size of the response built in memory. An attacker can craft a small request (within jute.maxbuffer) that references a large znode repeatedly, causing the server to materialize and retain all results in heap memory before serialization, exhausting the JVM and triggering an OutOfMemoryError. The vulnerability requires network access and no authentication to trigger.

## Affected products

- Apache ZooKeeper 3.7.0 through 3.9.6

## Timeline

- 2026-11-04: disclosed

## References

- [https://repo.maven.apache.org/maven2](https://repo.maven.apache.org/maven2)
- [https://lists.apache.org/thread.html/gj2vxwx8myq31js6tvb7bgls4nnxohj7](https://lists.apache.org/thread.html/gj2vxwx8myq31js6tvb7bgls4nnxohj7)

## Related threats

- [Apache ZooKeeper uncontrolled recursion in snapshot serialization](https://junglewise.ai/threats/cve-2026-115448-uncontrolled-recursion-in-apache-zookeeper-the-server-serializes)
- [Apache ZooKeeper quota subsystem denial of service](https://junglewise.ai/threats/cve-2026-100300-improper-handling-of-exceptional-conditions-in-the-quota)
- [Apache ZooKeeper improper authorization in SASL authentication](https://junglewise.ai/threats/cve-2026-100252-improper-authorization-vulnerability-in-apache-zookeeper-when)
- [Apache ZooKeeper setACL time-of-check time-of-use race condition](https://junglewise.ai/threats/cve-2026-100235-incorrect-authorization-due-to-a-time-of-check-to-time-of-use)
- [Apache ZooKeeper log injection via crafted add_auth request](https://junglewise.ai/threats/cve-2026-84501-apache-zookeeper-log-injection-via-crafted-add-auth-request)