# CVE-2026-102464: Eclipse Vert.x MQTT unbounded inbound QoS 2 message retention

Source: https://junglewise.ai/threats/cve-2026-102464-in-eclipse-vert-x-versions-4-0-0-4-5-34-or-5-0-0-5-0-12-or-5-1-0  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-15. Updated: 2026-10-20  
License: CC BY 4.0 with a link back

CVE-2026-102464 · Severity: medium · CVSS 5.9 · Published 2026-10-15

Eclipse Vert.x MQTT is a client library for MQTT messaging used in IoT and real-time applications. A malicious or compromised MQTT broker can send specially crafted messages that cause the client to retain them indefinitely without freeing memory, eventually exhausting available RAM and crashing the application or degrading its performance.

Technologies: [Eclipse Vert.X](https://junglewise.ai/threats/technologies/eclipse-vert-x). Vendors: [Eclipse](https://junglewise.ai/threats/vendors/eclipse).

## Quick answers

**Is CVE-2026-102464 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-102464 being exploited in the wild.

**How severe is CVE-2026-102464?** Medium severity, with a CVSS score of 5.9, published 15 October 2026.

**Which products and versions are affected?** Eclipse Vert.x MQTT 4.0.0 to 4.5.34, 5.0.0 to 5.0.12, 5.1.0 to 5.1.9, 5.2.0.

**Is there a fix for CVE-2026-102464?** Yes: fixed in 4.5.35, 5.1.10, 5.2.1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-102464 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-102464?** Check whether you run Eclipse Vert.X or Eclipse Vert.x MQTT 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 4.5.35, 5.1.10, 5.2.1

## Technical details

The vulnerability is an unbounded memory accumulation flaw in the MqttClient component. When processing inbound QoS 2 PUBLISH messages, the client stores them in an internal map (qos2inbound) awaiting PUBREL responses, but this map lacks size limits; an attacker can send QoS 2 messages with distinct packet identifiers while withholding PUBREL packets, causing indefinite retention of message payloads and metadata. The attack requires network access to the MQTT broker the client connects to; no authentication or user interaction is needed.

## Affected products

- Eclipse Vert.x MQTT 4.0.0 to 4.5.34, 5.0.0 to 5.0.12, 5.1.0 to 5.1.9, 5.2.0

## Timeline

- 2026-10-07: disclosed
- 2026-10-15: advisory

## References

- [https://github.com/vert-x3/vertx-mqtt/security/advisories/GHSA-46xj-5735-6qrp](https://github.com/vert-x3/vertx-mqtt/security/advisories/GHSA-46xj-5735-6qrp)
- [https://gitlab.eclipse.org/security/cve-assignment/-/work_items/344](https://gitlab.eclipse.org/security/cve-assignment/-/work_items/344)

## Related threats

- [Eclipse Vert.x STOMP FrameParser heap exhaustion](https://junglewise.ai/threats/cve-2026-118487-in-eclipse-vert-x-versions-4-0-0-4-5-35-or-5-0-0-5-2-2-the)
- [Eclipse Vert.x CachingWebClient cross-user cache disclosure](https://junglewise.ai/threats/cve-2026-118489-in-eclipse-vert-x-versions-4-0-0-4-5-35-or-5-0-0-5-2-2-when-one)
- [Eclipse Vert.x PostgreSQL client unbounded memory allocation](https://junglewise.ai/threats/cve-2026-103223-in-eclipse-vert-x-versions-4-0-0-4-5-34-or-5-0-0-5-0-12-or-5-1-0)
- [Eclipse Vert.x gRPC compression bomb denial of service](https://junglewise.ai/threats/cve-2026-102477-in-eclipse-vert-x-versions-4-0-0-4-5-34-or-5-0-0-5-0-12-or-5-1-0)
- [Eclipse Vert.x DB2 client unsafe Java deserialization in UDT handling](https://junglewise.ai/threats/cve-2026-102469-in-eclipse-vert-x-versions-4-0-0-4-5-34-or-5-0-0-5-0-12-or-5-1-0)