CVE-2026-8686
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.
CSIRTS triage
- What
- Missing bounds validation allows denial of service via crafted MQTT packets.
- Who is affected
- Users of coreMQTT version 5.0.0.
- Urgency
- Remediation is urgent due to the potential for service crashes.
- Action
- Upgrade to version 5.0.1 or later.
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Exploitation outlook
- Low exploitation risk0.39% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 31% of all EPSS-scored CVEs.
Advisory coverage (1)
- unknownCVE-2026-8686 - Heap out-of-bounds read in coreMQTT MQTT5 property parsingaws · 2026-06-05
External references
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