CVE-2026-8686 DoS from MQTT v5.0 Deserialization Fault in core MQTT
A missing bounds check in the MQTT v5.0 property parser allows a malicious broker to cause a denial of service in applications using the coreMQTT library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-8686?
CVE-2026-8686 is a high-severity denial of service vulnerability in FreeRTOS coreMQTT, published on 15 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-125
Which versions are affected by CVE-2026-8686?
It affects 1 product.
Products include Freertos Coremqtt.
How do I fix CVE-2026-8686?
No fix has been published for CVE-2026-8686 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-8686 being exploited?
There is no known exploitation of CVE-2026-8686 in the wild and no public exploit code.
Sources
Also known as GHSA-6qh9-r6jp-2wxc.