CVE-2026-8686 - Heap out-of-bounds read in coreMQTT MQTT5 property parsing

Bulletin ID: 2026-032-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 05/15/2026 11:45 AM PDT Description: coreMQTT is a lightweight MQTT client library for embedded devices. We identified CVE-2026-8686, an issue where missing bounds validation in the MQTT v5.0 SUBACK and UNSUBACK property parser in coreMQTT before 5.0.1 allows an MQTT broker to cause a denial of service (crash via heap out-of-bounds read) by sending a crafted packet. Impacted versions: v5.0.0 Please refer to the article below for the most up-to-date and complete information related to this AWS Security Bulletin.