CVE-2026-8686: Freertos Coremqtt

Critical severity, CVSS 9.1. EPSS: 0.7% chance of exploitation in the next 30 days.

Missing bounds validation in the MQTT v5.0 property parser in coreMQTT before 5.0.1 allows an MQTT broker to cause a denial of service by sending a crafted packet. To remediate this issue, users should upgrade to v5.0.1.

Affected products

• Freertos Coremqtt: version 5.0.0 only

Published 2026-05-15. Last modified 2026-06-17.