CVE-2026-102464
8.2HighPublished 15 Oct 2026 · NVD status: Undergoing Analysis · AI triage by gemini-3.8-flash
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
- Impact
- High impact on availability
- Weakness
- CWE-770
Impact
A malicious or compromised MQTT broker can crash your Vert.x application via out-of-memory denial of service. The broker only needs an active connection to your client to flood it with incomplete QoS 2 messages.
Root cause
The vertx-mqtt MqttClient stores inbound QoS 2 messages in an unbounded map while waiting for PUBREL packets without enforcing a size limit.
Affected systems
Eclipse Vert.x (io.vertx:vertx-mqtt) versions 4.0.0 through 4.5.34, 5.0.0 through 5.0.12, 5.1.0 through 5.1.9, and 5.2.0
CVSS v4.0 · 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Fix & remediation
Upgrade io.vertx:vertx-mqtt past the affected release ranges once vendor patches are available; if patching must wait, restrict client connections to trusted MQTT brokers only or avoid QoS 2 inbound subscriptions.
$ ./mvnw dependency:tree -Dincludes=io.vertx:vertx-mqttAI-suggested. Run it in staging first and check it against the vendor advisory. Why?
NVD 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.